DOI: 10.3897/j.moem.12.2.205799

Authors: Svetlana V. Stakhanova, Lyudmila A. Puntusova, Lidiya A. Gurchenkova, Elizaveta V. Shmakova, Ilya S. Krechetov, Lev V. Kozhitov

Abstract: Results of a systematic study of propylene carbonate (PC) based organic electrolytes with alkylammonium tetrafluoroborates for use in supercapacitors (SC) for portable electronics and self-charging power sources have been presented. The importance of the study is dictated by the requirement to combine SC high power capacity, electrochemical stability over a wide temperature range, and operation safety, especially in independent miniaturized devices. Unlike acetonitrile (AN) conventionally used in SC electrolytes, PC is not noxious and non-flammable, but its high viscosity limits the electrical conductivity of electrolytes thus making the choice of optimum ionogenic salt a critical task. The properties of PC-based electrolytes with tetraethylammonium (TEA·TFB), methyltriethylammonium (TEMA·TFB), spiro-(1,1’)-bipyrrolidinium (SBP·TFB), and 1,1-dimethylpirrolidinium (DMP·TFB) tetrafluoroborates, differing in the size and structure of cations (acyclic and cyclic) have been studied. All the test salts deliver approximately similar capacities of SC cells, but TEA·TFB demonstrates somewhat lower capacity due to the large size of its cation. Ionogenic salts with cyclic cations (SBP·TFB and, especially, DMP·TFB) provide a far greater range of operation voltage at elevated temperatures to 85 °C, whereas TEA·TFB and TEMA·TFB electrolytes degrade at above 60 °C. Durability tests (up to 70,000 cycles at 50–95 °C) confirmed the electrochemical and thermal stability of DMP·TFB+PC: SC cells with the latter electrolyte retain 80 % of initial capacity after 50,000 cycles of galvanostatic charging/discharging (GCD) and provide for an operation voltage of 3.0 V. The recommended operation temperature range for SC with DMP·TFB+PC electrolyte is 0 to 85 °C, with the possibility of short-time temperature growth to 95 °C, whereas at below 0 °С the growing viscosity of the electrolyte causes a dramatic degradation of SC capacity. Thus, DMP·TFB+PC electrolyte is promising for SC used in portable electronics.

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DOI: 10.3897/j.moem.12.2.205937

Authors: Alexey V. Ershov, Daniil A. Yushkov, Mikhail E. Suvorov, Anton V. Zdoroveyshchev, Nikolay V. Baidus

Abstract: The effect of rapid thermal annealing (RTA) at 950 and 1000 °C for 3 min on the photoluminescence (PL) in multilayered (~50 layers) nanoperiodical (4/3 nm) a-SiOx/SiO2 and a-SiOx/ZrO2 nanostrucutres (MNS) synthesized using vacuum evaporation has been analyzed in comparison with conventional long-term (~1 h) high-temperature annealing (HTA). It has been shown that the use of sequential anneals (RTA + HTA) at 1000 and 1100 °C, respectively, allows increasing the intensity of the PL band of silicon nanocrystals (at ~800 nm) by 2.5 times as compared with conventional heat treatment. Analysis of the PL spectra suggests that RTA triggers the formation of chain and ring non-phase silicon inclusions and/or small-sized Si nanocrystals (~2 nm) which generate radiation near 600 nm at room temperature. Thus, one can conclude that RTA produces elevated concentrations of the abovementioned silicon nuclei which, upon subsequent HTA, serve as growth centers for larger Si nanocrystals (~3–4 nm). It has been found that SiOx/ZrO2 MNS exhibit a similar behavior (qualitative) of PL spectra after RTA. However, the PL intensity in this case is 5–10 times lower, due to the chemical interactions between the materials of the MNS layers with the formation of zirconium silicides and silicates.

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DOI: 10.3897/j.moem.12.2.181662

Authors: Zyad Attia Dawood, Abdulkhaliq A. Sulaiman, Hanaa E. Jasim

Abstract: Electrochemical etching was performed in a highly acid-resistant Teflon electrochemical cell. A current density of 15 mA/cm² was applied using the silicon samples as the cathode. These samples were fixed and immersed in an etching solution composed of 18 % hydrofluoric acid mixed with ethanol. The ethanol facilitated the removal of hydrogen bubbles generated during etching, enabling the formation of regular and uniform pores. Carbon films with thicknesses of 20 nm and 50 nm were deposited onto the porous silicon (PSi) surface via plasma spraying from carbon rods. Raman spectroscopy of the 20 nm carbon-porous silicon junction revealed peaks corresponding to carbon nanotubes at 170, 1402, and 1533 cm-1, while peaks associated with porous silicon appeared at 554, 977, 1154, 2940, and 3363 cm-1. For the 50 nm carbon film, the Raman spectrum of the PSi/CNT junction exhibited carbon nanotube peaks at 190, 1407, and 1540 cm-1, and silicon peaks at 564, 1000, 1144, 2945, and 3366 cm-1. X-ray diffraction spectra of the PSi/CNT junction showed sharp peaks at 28.62° and 28.15° for carbon nanotubes in the 20 nm and 50 nm films, respectively. Electrical characterization demonstrated that PSi-CNT junctions exhibited lower current flow under dark conditions compared to Si-CNT junctions. However, increasing the carbon layer thickness enhanced the electrical conductivity of the junctions under both dark and illuminated conditions. This improvement is attributed to the greater amount of carbon anchored on the porous silicon matrix as the thickness of the deposited carbon layer increases.

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DOI: 10.3897/j.moem.12.2.194213

Authors: Tatiana S. Ilina, Sofia V. Torianik, Dmitrii S. Zakhidov, Dmitry A. Kiselev

Abstract: This work puts forward an interpretable approach for predicting ferroelectric properties on the basis of sure independence screening and sparsifying operator (SISSO) method, which uses a symbol regression for studying mathematically compact expressions having explicit physical sense. In combination with ensemble machine learning (ML) methods, i.e., extra trees regressor (ETR), random forest (RF), gradient boosting regressor (GBR), and extreme gradient boosting (XGBoost), as well as SHAP (SHapley Additive exPlanations) analysis for the selection and interpretation of features, the approach developed in this work simultaneously delivers high prediction accuracy and possibility to study fundamental mechanisms underlying the formation of ferroelectric properties in materials. Based on the available experimental data for 476 potassium-sodium niobate (KNN-based) ceramic specimens, feature engineering has been carried out, as a result of which the key physical descriptors have been separated and the optimal choice of predictors has been determined. The model developed herein allows explicit, i.e., in a formularized form, description of quantitative relationships between structural parameters and functional characteristics of materials. The methodological approach to interpretable machine learning put forward in this work opens up new possibilities for the optimization-driven design of piezoelectric ceramics and other functional materials, and will be useful both for fundamental research and practical applications.

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DOI: 10.3897/j.moem.12.2.205390

Authors: Konstantin V. Feklistov, Aleksey G. Lemzyakov, Demid S. Abramkin, Kirill A. Svit, Alexey M. Pugachev, Vladimir A. Volodin, Denis V. Marin, Evgeny V. Spesivsev, Ivan A. Azarov, Leonid N. Safronov, Sergey A. Kochubey, Kirill S. Ershov, Aleksandr V. Kapishnikov, Alexander N. Shmakov, Alexander A. Shklyaev, Yuriy A. Zhivodkov

Abstract: In2O3 : Er films were synthesized on silicon substrates by the RF magnetron sputter deposition. The solid solution ((In1-xErx)2O3) is formed here. The 1.534 µm erbium electroluminescence is observed by the current through the investigated heterostructure substrate-n-Si\In2O3 : Er-film\ITO-contact. The Er excitation model by the electron-hole recombination is proposed as follow. The electron current flows at the indium oxide conduction band. And the hole current flows at the channel in the middle of the In2O3 : Er bandgap. The hole channel is formed by the defect state density spreading from the valence band edge into the bandgap. Therefore the electron-hole recombination energy is lower than the indium oxide bandgap and equals to the 1.56 eV. Then the electron-hole recombination excites in resonance the third excited state of Er3+ 4I9/2 (1.53 eV). Then the nonradiative relaxation to the first excited state 4I13/2 (0.81 eV) occurs. And finally the 1.534 µm radiative emission into ground state 4I15/2 occurs.

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DOI: 10.3897/j.moem.12.1.147738

Authors: M. Vanitha Sri, V. T. Jeielayaganga, D. Sakthilatha

Abstract: This review explores the role of conductive polymers in enhancing the performance of electrochemical supercapacitors, a promising solution for sustainable energy storage. Supercapacitors close the distance between batteries and conventional capacitors, providing quick charge-discharge cycles, a high energy density, and extended cycle life. The study delves into key types of supercapacitors, including electric double-layer capacitors, pseudocapacitors, and hybrid systems. Conductive polymers like polyaniline, polypyrrole, polythiophene, and poly (3,4-ethylene dioxythiophene) are emphasized for having exceptional electrochemical qualities, flexibility, and cost-effectiveness. However, these materials face challenges related to mechanical stability, cycle life, and ion transport efficiency. Future opportunities lie in developing hybrid materials, nanostructured designs, and scalable synthesis methods to enhance conductivity, stability, and storage capacity. This comprehensive review underscores the potential of conductive polymers in advancing next-generation energy storage technologies to meet growing global energy demands.

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DOI: 10.3897/j.moem.12.1.182531

Authors: Vladimir G. Kostishin, Albert A. Alekseev, Sergey V. Scherbakov, Aleksey G. Nalogin, Vitaliy A. Turchenko, Igor M. Isaev, Elena S. Savchenko, Alexander G. Savchenko, Boris M. Skibo, Ekaterina O. Matashneva

Abstract: Hexagonal strontium ferrite has found wide application in the fabrication of permanent magnets and active media of UHF electronics and photonics. The performance of hexagonal strontium ferrites depends largely on their synthesis method. Hexagonal polycrystalline isotropic SrFe12O19 ferrite specimens have been synthesized using fast electron beam radiation-thermal sintering (RTS) in a PLU-6 electron accelerator of G.I. Budker Institute of Nuclear Physics of the Russian Academy of Sciences. The RTS temperature has been varied from 1200 to 1400 °C, and the RTS time, from 10 to 90 min. The phase composition and lattice parameters of the specimens have been studied using X-ray diffraction on a DRON-8 diffractometer in CoKα1 radiation. The density of the specimens has been measured following Archimedean law on a UW620H electronic balance with a liquid density measurement attachment. The magnetic hysteresis loop parameters of the specimens have been studied with a VM-07 vibromagnetometer. The specimens has proven to be single-phase with a P63/mmc space group (No. 194), corresponding to a hexagonal ferrite structure. For the first time, changes in the magnetic hysteresis loop parameters of hexagonal SrFe12O19 strontium ferrite specimens synthesized with fast electron beam RTS have been studied. We show that the width and intensity of the magnetic hysteresis loop decrease noticeably with an increase in the RTS temperature from 1200 to 1350–1400 °C. The magnetization coercive force jHc decline to the minimum values at RTS temperatures Tsint ≥1250 °C, probably due to recrystallization in the ferrite lattice: the combined impact of RTS temperature and radiation-induced diffusion triggers intense grain growth, significantly reducing the number of domain boundaries and, hence, causing a drop in jHc. The high energy efficiency of RTS in ferrite ceramics synthesis has been confirmed for the example of SrFe12O19.

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DOI: 10.3897/j.moem.12.1.189317

Authors: Artyom A. Sharapov, Alexey V. Sidelev, Konstantin I. Tapero, Artyom E. Zemtsov

Abstract: Results of focused laser irradiation of semiconductor structures having relatively small sizes of discrete components on the crystal were presented. Different laser beam depth profiles were obtained in the experiments via different lenses. The focused beam size was varied in a range of 1.4 to 3.6 μm at the beam waist. The test specimens were position-sensitive detectors with small pixel size (~15 μm). We showed that the use of different lenses with constant pulse energy and duration yields different results in sensitivity assessment. Conclusions were made as about the limitations in the application of precision irradiation methods to semiconductor structure.

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DOI: 10.3897/j.moem.12.1.154196

Authors: Sanjay Awasthi, Dinesh Kumar Chitriv

Abstract: After discovery of ferroelectric properties of NaNO2, it was classified as order disorder type ferroelectric material based on earlier studies. Along with this and result carried out from our recent theoretical analysis of electric field gradients due to quadrupolar nucleus 23Na in this crystal clearly indicate the presence of another type of local motion with reorientation of NO2 groups during polarization reversal. It is the displacement of Na atom in crystalline space with considerable amount. For this we have obtained ratios; M1111/M3333 = 0.71, M1133/M3333 = –0.74, M2323/M3333 = 0.07, M3131/M3333 = 0.17, M1212/M3333 = 0.17 of M-tensor components by using point charge model. Their values are found for flipping angle 172° w.r.t. direction specified by direction cosines l1 = 0.996, l2 = 0.075, l3 = 0.0486 of NO2 groups and displacement of Na atom in c-, a-, b-crystalline space dc = 0.015 nm, da = –0.046 nm, db = 0.048 nm. Values of these ratios of M-tensor components are found in very good agreement with NMR experimental values of MTR’s measured by earlier researchers. For these theoretical values of M-tensor ratios, we have found minimum value of sum of square deviation S (=0.0070). This analysis confirmed the possibility of displacive nature with order disorder nature of NaNO2 ferroelectric material. A study based on XRD analysis of NaNO2 by M. Ichikawa et al. (2002) also confirmed that the ferroelectric transition of NaNO2 is not of pure order-disorder type.

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DOI: 10.3897/j.moem.12.1.166784

Authors: Mustapha Ammari, Mohamed Jabha, Mohamed Yaakoubi, Samira Kharchouf, Abdellah Elalaoui, El Houssine Mabrouk

Abstract: Perovskite solar cells (PSC) are a promising alternative to silicon cells, achieving a power conversion efficiency of 25.8% in ten years. Research on alternatives is necessary. Phthalocyanines, multifunctional materials, have attracted interest in improving PSCs. Used as a hole transport material (HTM), they offer an alternative to spiro-OMeTAD and PTAA due to their low cost, stability, and electronic properties. This work optimizes zinc phthalocyanine (ZnPc) and triphenylamine zinc phthalocyanine (TPA-ZnPc) molecules using DFT (B3LYP/6-311G (d,p)) to analyze the effect of triphenylamine substitution. Adding triphenylamine modifies molecular geometry and reduces hole transport capacity. The bandgap energies are 2.178 eV (ZnPc) and 2.062 eV (TPA-ZnPc). Although both absorb in the visible range, TPA-ZnPc exhibits enhanced absorption. ZnPc demonstrates strong potential as an hole transport material with MAPbI3.

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DOI: 10.3897/j.moem.12.1.181500

Authors: Ilya V. Kubasov, Andrei V. Turutin, Aleksandr A. Temirov, Alexander M. Kislyuk, Viktor V. Kuts, Vladimir P. Ivanov, Evelina E. Maksumova, Elena A. Skryleva, Mikhail D. Malinkovich, Yury N. Parkhomenko

Abstract: Reliable electrical contacts are essential for high-temperature piezoelectric devices based on lithium niobate (LiNbO3, LN), yet the behavior of electrode materials under elevated temperatures remains insufficiently studied. Here we evaluate three practical electrode systems on bidomain LN (BLN) substrates: screen-printed Pd thick films, sputtered indium–tin oxide (ITO), and sputtered nichrome (80 wt.% Ni and 20 wt.% Cr). Bidomain LN crystals function as single-crystal piezoelectric bimorphs with well-defined bending resonances, enabling sensitive impedance-based detection of electrode degradation. Impedance spectra were recorded in 100 °C increments up to 800 °C, complemented by microstructural inspection, electrical resistivity measurements, and X-ray photoelectron spectroscopy. Pd thick films showed the highest stability, with unchanged impedance spectra after heating to 800 °C and cooling. Indium–tin oxide electrodes remained functional up to at least 700 °C, with possible operation at 800 °C. X-ray photoelectron spectroscopy results suggest gradual incorporation of Nb from the BLN substrate which may initiate slow degradation in ITO. NiCr electrodes showed degradation of electrical contact near 500 °C due to oxide formation, while intrinsic electrical degradation associated with loss of film continuity occurred above 600 °C. These results identify Pd as a robust but costly choice, ITO as a promising mid-range alternative, and NiCr as suitable only within a lower high-temperature window.

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DOI: 10.3897/j.moem.11.4.157750

Authors: Syed Md. Ikram, Md. Arafat Rahman, Md. Muktadir Billah, Jesia Alam Jui

Abstract: Nanostructured copper oxides (CuO, Cu2O) are regarded as promising anode materials for lithium-ion batteries (LIBs) due to owing high theoretical specific capacity and efficient conversion reaction mechanism with lithium under moderate conditions. On investigating the cyclic characteristics of binder-free CuO/Cu2O anodes at 1C current rate, first charge and discharge capacities were observed to be 455.4 and 431.9 mAh/g, respectively, with a Coulombic efficiency of 94.8 %. However, a gradual mitigated capacity was evident as the discharge capacity was decreased to 352.2 mAh/g by the 20th cycle, which can be attributed to solid electrolyte interphase (SEI) layer formation, electrode degradation, or loss of lithium. Beyond 20th cycles, the battery exhibited a more stable cycling regime, with Coulombic efficiency stabilizing ranging around 82–85 %. By the 40th cycle, discharge capacity was further declined to 339 mAh/g, indicating the ongoing degradation mechanisms, however at a much lower rate, such as SEI layer thickening and electrode pulverization. However, despite the initial instability, the system demonstrated enhanced consistency in later cycles, emphasizing the potential of nanostructured copper oxides as efficient LIB anodes. Future efforts should focus on mitigating long-term capacity fading to enhance performance and cycle life.

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DOI: 10.3897/j.moem.11.4.180460

Authors: Kira L. Еnisherlova, Yury V. Kolkovsky, Vladimir T. Nikolenkov, Semen A. Kapilin

Abstract: This paper analyzes properties of the dielectric/AlGaN/GaN system with an ALD Al2O3 film as a dielectric. It was investigated how the current flow process in the system changes due to the deposition of films with different thicknesses; at what bias voltage the electron emission process from the boundary states begins, and how the properties of the barrier layer in the initial heterostructure affect the parameters of the current in the system. It was found that a positive charge forms at the Al2O3/AlGaN interface, the charge magnitude increasing with the film thickness. It was also shown that film deposition affects the charge magnitude in the channel. It was demonstrated that the frequency at which C–V measurements are carried out affects Dit, i.e., the distribution of the electron states at the boundaries of the Al2O3/AlGaN/GaN system. It was shown that the density of the detected donor-like states increases abruptly with an increase in the measurement frequency. It was furthermore demonstrated that a correctly chosen measurement scheme allows one to estimate the potential contribution of the two boundaries, i.e., AlGaN/GaN and Al2О3/AlGaN, in this case, some of the electrons may remain in the channel.

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DOI: 10.3897/j.moem.11.4.152006

Authors: Nikolay A. Bosak, Maxim V. Bushinsky, Liudmila V. Baran, Victoria V. Malyutina-Bronskaya, Olga S. Mantytskaya, Hanna S. Kuzmitskaya

Abstract: Nanostructured thin films on silicon and glass substrates have been synthesized by high-frequency pulse-periodic action of laser radiation with a wavelength of 1.064 μm. The morphology of La0.5Sr0.5Co0.9Ni0.1O3 thin films investigated using atomic force microscopy showed that films with a developed surface structure have been obtained. Transmission spectra of La0.5Sr0.5Co0.9Ni0.1O3 films were obtained in the visible, near and mid-IR regions. The maximum transmittance of the laser-deposited La0.5Sr0.5Co0.9 Ni0.1O3 film on silicon is observed in the near IR region of the spectrum and reaches the value of 59 % at a wavelength of λ = 1182 nm. Electrophysical characteristics of La0.5Sr0.5Co0.9Ni0.1O3/Si structures were analyzed. When measuring the longitudinal current-voltage characteristic of the La0.5Sr0.5Co0.9 Ni0.1O3/Si structure under the influence of laser radiation with a wavelength from 405 nm to 1064 nm (at a voltage of more than 1.5 V), a photoelectric effect have been observed. The measured capacitance-voltage characteristics of the studied structure have demonstrated the photo-ferroelectric properties.

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DOI: 10.3897/j.moem.11.4.171888

Authors: Andrey I. Protsenko, Viktor A. Korzhov, Ivan I. Petrov, Yan A. Eliovich, Ilya V. Kubasov

Abstract: Within the framework of a fast double-crystal synchrotron monochromator based on adaptive X-ray optics elements–ABXO (Adaptive Bending X-ray Optics) prototype developing, the possibility of its use as a fast X-ray shutter was demonstrated. This work proposes two operational modes for the shutter, which differ in the generated X-ray pulses parameters and depend on the ABXOs operating mode. Achievable temporal parameters of the generated X-ray pulses were estimated and the prospects for their application in time-resolved X-ray research methods are considered.

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DOI: 10.3897/j.moem.11.4.151665

Authors: Pavel V. Sheuchyk, Aliona V. Stanchik, Valery F. Gremenok, Konstantin P. Buskis, Benik L. Hovsepyan, Ashot M. Khachatryan, Stepan G. Petrosyan

Abstract: The effect of substrate temperature and laser wavelength on the laser deposition of CdTe thin films has been studied. CdTe thin films synthesized on glass substrates have been studied using X-ray spectral microanalysis, X-ray diffraction and scanning electron microscopy. It has been shown that the ratio of elements in the CdTe thin films depends on both the substrate temperature and the laser wavelength. Specific features of the crystalline structure, phase composition and structural parameters of the synthesized CdTe films depending on the deposition process conditions (substrate temperature 100–400 °С, laser wavelength 600–1200 nm) have been revealed. Specifically, CdTe thin films deposited using laser radiation of wavelengths of 600 and 1200 nm have a cubic crystalline structure, while CdTe films obtained at a laser wavelength of 1064 nm have either a hexagonal structure or are a mixture of cubic and hexagonal phases, depending on the substrate temperature. At a low substrate temperature (100 °C) the films crystallize to a hexagonal structure, whereas at higher temperatures (200, 300 and 400 °C) the films are a polycrystalline mixture of cubic and hexagonal CdTe phases, growing predominantly along the [111]C direction. It has been shown that CdTe thin films on glass substrates have similar morphologies but different thicknesses, regardless of deposition conditions.

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DOI: 10.3897/j.moem.11.4.174536

Authors: Mamadou Tamboura, Ekaterina A. Gosteva, Maxim V. Chichkov

Abstract: The influence of prolonged ultraviolet (UV) irradiation on the structural and functional properties of graphene deposited on copper, silicon, and poly(butyl methacrylate) (PnBMA) substrates has been investigated. Using Raman spectroscopy, it was shown that UV exposure induces various types of defects, the nature of which is determined by both the substrate type and the number of graphene layers. It was established that for the transferred PnBMA/Gr1 and PnBMA/Gr2 coatings, a significant increase in specific surface resistance is observed after irradiation, with more pronounced degradation of conductivity being characteristic of the PnBMA/Gr2 sample with fewer graphene layers. It is important to note that despite the increase in resistance, its values for all studied "graphene-PnBMA" coatings remained within the antistatic range (104–1012 Ω/sq) throughout the experiment. The incorporation of commercial graphene nanoparticles into the PnBMA matrix (NP-Gr/PBMA) significantly enhances stability: the composite maintained antistatic properties (resistance of 2–3 kΩ/sq) even after 168 h of irradiation. A critical effect of UV exposure is the transition of the coating surfaces from a hydrophobic to a hydrophilic state due to the photo-oxidation of graphene, which was particularly pronounced in the PnBMA/Gr1 sample. The results demonstrate that the stability of graphene-containing coatings under UV irradiation is determined by the number of graphene layers and the properties of the substrate.

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DOI: 10.3897/j.moem.11.4.175359

Authors: Aleksandra S. Kim, Natalya A. Perevedentseva, Sergey Yu. Yurchuck, Fedor D. Korzhov

Abstract: The effect of rapid thermal annealing in H2 atmosphere on the ohmic properties of contacts on the basis of two-layered transition metals (e.g. Ti, Ni, Pd and Cr) and Au compositions on р+-Si has been studied. It has been shown for the example of two-layered Ti/Au compositions that rapid thermal annealing in H2 atmosphere at 340 °C for 20 s provides for an ohmic contact with lowest specific resistivity due to the formation of silicides at the Si/Me interface (Me = Ti, Ni, Pd and Cr). The applicability of the process in silicon diode technology for reducing the series resistance and increasing the device yield has been confirmed for small contact area commercial p+–n clamping diodes. Furthermore, the effect of rapid thermal annealing in H2 atmosphere on the level of reverse dark currents in highly ohmic p-Si photodiode has been studied. The results for the commercial p–i–n silicon multi-pad photocells suggest an improvement of the dark currents of the photosensitive pads and the guard ring after rapid thermal annealing in H2 atmosphere at 450 °C for 5 s and an increase in the device yield. This can be attributed to the hydrogen saturation of the dangling silicon bonds, providing for a decrease in the density of the surface states and stabilization of the charge properties at the SiO2/p-Si interface. The applicability of rapid thermal annealing in H2 atmosphere for dark current reduction in highly ohmic p-Si photodiode technology has been confirmed.

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DOI: 10.3897/j.moem.11.3.152137

Authors: Tatiana S. Ilina, Sofia V. Torianik, Dmitrii S. Zakhidov, Evgeniya L. Buryanskaya, Anatoly V. Pavlenko, Ekaterina V. Barabanova

Abstract: Replacement of highly noxious led zirconate titanate based materials in MEMS applications for environmentally safe materials remains an important task. Complex multicomponent doping of KNN ceramics provides for a significant improvement of their ferroelectric properties. The efficiency of different machine learning (ML) methods in the prediction of piezoelectric coefficient of KNN-based ceramics has been analyzed. ML integration allows one to accelerate the development of new materials and identify latent interdependences between their composition, structure, and properties. To understand the mechanisms of relationship between the composition and properties, we used the Sure Independence Screening and Sparsifying Operator (SISSO) method in combination with regression ML methods, such as Support Vector Regression, Ridge, Lasso, Elastic Net, Xtreme Gradient Boosting, Random Forest, Gradient Boosting Regression, and Extreme Tree Regression. The Gradient Boosting Regression (GBR) method proved to be the most efficient in combination with SISSO. The test sampling accuracy reached 81 %, and GBR validation for experimental data delivered a mean absolute error of 26 pC/N.

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DOI: 10.3897/j.moem.11.3.143013

Authors: Igor A. Belyakov, Mikhail D. Kochergin, Ilya A. Solovyov, Vladimir G. Kurbatov, Anna A. Gavrilova, Denis V. Vertyanov

Abstract: The article describes the preparing process for composites with a polyimide varnish PILK-2B matrix, which filled with particles of technical diamond, copper oxide, cubic boron nitride and hexagonal boron nitride for use in redistribution layers during chip packaging. Article show the results of the adhesive properties study for these composites with various fillers in relation to alkali glass and ST50 sitall substrates using the pull-off method. The measurement showed that the maximum adhesion to sitall and glass substrates is characteristic of the composite based on cubic boron nitride. It is 20.97 MPa and 20.11 MPa, respectively. Composites based on technical diamond and hexagonal boron nitride show lower adhesion – 17.48 and 18.03 MPa for sitall, 17.27 and 16.84 for glass. The material based on copper oxide show a significant difference in adhesion for sitall and glass – 14.78 MPa and 19.65 MPa, respectively. In addition, the article presents the results of composite processing using infrared nanosecond laser ablation to obtain structures in the form of traces and cylinders (contact pads) of various sizes. Cubic boron nitride based composites show clearest pattern with minimum line/space parameter of 25 µm and minimum delamination. Composite based on hexagonal boron nitride show the worst result with the maximum number of damages and flakes during laser treatment.

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DOI: 10.3897/j.moem.11.3.143304

Authors: Anna O. Diteleva, Dmitry Yu. Kukushkin, Vladimir V. Sleptsov

Abstract: This work is devoted to the development of an electrode material for energy storage devices and its nanostructuring technology, which significantly improve energy characteristics. The electrode material consists of a conductive carbon flexible matrix with a high specific surface area filled with silver nanoparticles measuring 10–40 nm. The design and manufacturing technology of a supercapacitor based on an aqueous electrolyte with an operating voltage of 2.6 V and a specific energy consumption of 5.5 Wh/kg are presented.

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DOI: 10.3897/j.moem.11.3.163093

Authors: Dmitriy G. Muratov, Lev V. Kozhitov, Irina V. Zaporotskova, Vladimir V. Sleptsov, Artem V. Zorin, Alena V. Popkova, Nikita I. Nikitenko, Andrey A. Vasilev, Ivan V. Silaev

Abstract: Herein, we report a systematic investigation of the synthesis methodology, structural characteristics, and electrochemical performance of CoMn/C metal-carbon nanocomposites derived via IR pyrolysis from manganese-substituted metal-organic frameworks (MOFs) exhibiting ZIF-67 topology. The MOF precursors were synthesized utilizing a chemical co-precipitation approach in aqueous media under ultrasonic treatment, with systematic variation of Co:Mn molar ratios ranging from 95:5 to 50:50, employing 2-methylimidazole as the organic linking agent. X-ray diffraction analysis coupled with electron microscopy investigations revealed that manganese incorporation into the cobalt sites is feasible up to a Co:Mn ratio of 70:30 while maintaining the intrinsic ZIF-67 crystalline architecture, concomitantly leading to a systematic reduction in crystallite dimensions from 36 to 21 nm and corresponding morphological modifications. The subsequent IR pyrolysis conducted within the temperature range of 500–700 °C yielded metal-carbon nanocomposites comprising homogeneously dispersed Co, MnO2, and Mn3O4 nanoparticles within a porous carbonaceous matrix. Electrochemical characterization demonstrated optimal specific capacitance values of 336 F/g at 0.25 A/g current density for nanocomposites exhibiting Co:Mn ratio of 80:20, synthesized at the optimal pyrolysis temperature of 600 °C. The resultant materials exhibited exceptional cycling stability, maintaining capacitance retention exceeding 95 % through 1000 charge-discharge cycles, while demonstrating robust performance across a broad potential window up to 1.4 V in 6M KOH aqueous electrolyte. The enhanced specific capacitance values are attributed to the synergistic contribution of double-layer capacitance from the developed porous carbon framework and pseudocapacitive effects arising from reversible redox processes of metallic nanoparticles and their corresponding oxides. These findings elucidate the significant potential of Mn-substituted MOFs as precursors for the fabrication of high-performance electrode materials in symmetric supercapacitor applications, exhibiting superior electrochemical characteristics.

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DOI: 10.3897/j.moem.11.3.150783

Authors: Yan A. Eliovich, Andrey I. Protsenko, Viktor A. Korzhov, Rashid R. Fakhrtdinov, Anton G. Kulikov, Anatolii A. Mololkin, Yuriy V. Pisarevsky, Mikhail V. Kovalchuk

Abstract: Based on previously proposed approaches for implementing monochromatic X-ray beam rapid spectra modulation method using adaptive X-ray optical elements, a new spatially resolved technique has been developed. This technique was applied to record the tantalum L3 edge absorption spectra linear distribution with 37 µm spatial resolution. This method accelerates the sample's structure study rate by increasing the illuminated area compared to the classical X-ray absorption spectroscopy method and increasing the volume of information obtained relative to X-ray fluorescence. This approach is promising for studying crystalline materials with complex structure used in the microelectronics industry.

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DOI: 10.3897/j.moem.11.3.150265

Authors: Lusine S. Elbakyan, Irina V. Zaporotskova

Abstract: The development of nanotechnology requires more advanced computer modeling methods to study the properties of nanoparticles and clusters. These particles are the main “building material” in nanotechnology, determining the unique properties of the created products. Computer modeling makes it possible to predict the behavior of nanoparticles, their interaction with the environment and with each other, as well as optimize the processes of their synthesis and application. Due to their lightness and flexibility, conductive polymers open up new possibilities for the development of flexible and wearable electronics. Currently, research is quite widespread on the creation of new polymer materials, which are obtained by modifying known polymers with various fillers, including nanomaterials. One of the well-known nanomaterials is carbon nanotubes. The existing applications of nanotubes are almost limitless. In this work, the well-known polymer polyvinyl alcohol and carbon nanotubes are chosen as the main objects. A theoretical study of the possibility of creating a stable Polymer-CNT complex using the quantum chemical calculation method DFT has been performed. Single- and double-walled carbon nanotubes were used in the study. The mechanism of interaction of nanotubes with fragments of polyvinyl alcohol has been studied. The electron-energy structure of the obtained polymer nanocomposites is analyzed and a conclusion is made about the conductive properties of the resulting complex.

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DOI: 10.3897/j.moem.11.3.143766

Authors: Petr Ershov, Alexander Omelyanchik, Pavel Vorontsov, Abdulkarim Amirov, Azamat Zhansitov, Ismel Musov, Khasan Musov, Svetlana Khashirova, Valerii Savin, Artem Ignatov, Larissa Panina, Valeria Rodionova

Abstract: In this paper, we have investigated piezoelectric, magnetic and magnetoelectric properties of composite materials, consisting of polyvinylidene fluoride (PVDF) matrix and CoFe2O4 nanoparticles in the form of filament extrusion and 3D printed films. We used PVDF powders from different manufacturers each with different molecular weights and phase compositions. For PVDF with lower molecular weight and higher electroactive phase content of the, we observed that approximately 80 % of the electroactive phase in the starting polymer was effectively transferred to the printed films through all technological stages. The composite filaments exhibited ferromagnetic behavior with a large coercive force of 1.7±0.1 kOe consistent with a particle size of about 20 nm. The magnetoelectric coefficient was about 2 mV/(Oe∙cm) for printed composite films from both precursors, which is sufficient for a range of applications including microelectronics and tissue engineering using magnetically stimulated electric fields.

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DOI: 10.3897/j.moem.11.2.137432

Authors: P. Harikrishnan, P. Sivakumar

Abstract: This study presents a comparative performance analysis of GaAs, InP, and GaN-based MOSFETs using Spreading Resistance Profiling (SRP), Capacitance–Voltage (C–V) simulation, and Finite Element Analysis (FEA) within a sentaurus technology computer-aided design (TCAD) environment. The results show that GaN MOSFETs achieve the highest on-current (450 µA) and peak gm (400 µS), but exhibit a slightly higher ON-resistance (5 Ω) compared to GaAs (4.44 Ω) and InP (4.21 Ω). In terms of VTH uniformity, GaN demonstrates superior dopant stability with the lowest standard deviation (0.143 V), followed by InP (0.213 V) and GaAs (0.266 V). These findings highlight the trade-offs between current drive, resistance, and variability among III–V materials, with GaN offering strong performance and reliability characteristics suitable for secure and thermally stable semiconductor applications.

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DOI: 10.3897/j.moem.11.2.142503

Authors: Abdulkarim A. Amirov, Maxim D. Popov, Timur R. Nizamov, Elizaveta S. Permyakova, Tatiana S. Ilina, Andrei V. Turutin, Olga A. Guselnikova, Dmitry A. Kiselev, Yuri N. Parkhomenko

Abstract: The smart thermoresponsive composite of PNIPAM/FeRh by chemical grafting of PNIPAM polymer on substrate of FeRh alloy were fabricated and studied. The characteristic peaks at 1690 (C=O), 2480–3000 (CH), and 3280 (N–H) observed on IR-FTIR spectra of PNIPAM/FeRh corresponded to the functional groups of PNIPAM and confirmed grafting of the polymer on the surface of FeRh substrate. The measurements of wetting demonstrated the changes of contact wetting angle from 69.3±1.5° at 27 °C to 76.9±1.2° at 40 °C attributed with transformation of PNIPAM polymer from the hydrated to the dehydrated state due phase transition with lower critical temperature at ~32 °C. The changes in surface topography of PNIPAM polymer in results of phase transition with lower critical solution temperature in PNIPAM were observed using atomic force microscopy measurements in temperature range 30–50 °C in heating and cooling.

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DOI: 10.3897/j.moem.11.2.143172

Authors: Anton Anikin, Alena Shumskaya, Anna Motorzhina, Anastasia Gurevich, Sergey Bedin, Ilia Doludenko, Dinara Khairetdinova, Victor Belyaev, Kateryna Levada, Valeria Rodionova, Larissa Panina

Abstract: Anisotropic ferromagnetic micro- and nanoparticles made of 3d metals demonstrate the ability to effectively influence micro- and nanoscale biological entities through hyperthermia and mechanical vibrations induced by magnetic fields. Multifunctional nanoparticles designed for combined therapies are particularly effective. This study explores the potential application of Ni@Au nanotubes to synergize magnetomechanical effects with photothermal heating. The orientation of nanotubes in a magnetic field was demonstrated by changes in the intensity of the light beam passing through a water suspension of nanotubes. The gold coating doubled the optical absorption of the solution in comparison with pure nickel nanotubes and resulted in the appearance of a resonance-enhanced peak in the range of 700–800 nm, the position of which is in accordance with theoretical calculations. The photothermal performance of nanotube solu-tions was quantitatively assessed by determining the photothermal conversion coefficient, which increased due to gold coating. However, it’s worth noting that the gold coating did not significantly reduce nanotube cytotoxicity in hepatocyte-derived cellular carcinoma cells (Huh7). The potential reasons for this outcome include the large particle size and non-uniform gold coating. Nevertheless, the combination of two anti-cancer therapies employing the same type of particles offers the opportunity to reduce particle concentration while maintaining the required therapeutic efficacy.

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DOI: 10.3897/j.moem.11.2.143665

Authors: V.T. Jeielayaganga, R. Keerthiga, M. Venkatesh

Abstract: Carbon-based materials have emerged as attractive possibilities for supercapacitor applications due to their high electrical conductivity, huge surface area, and excellent stability. The potential of carbon materials, like carbon allotropes and activated carbon derived from biowaste, to enhance supercapacitor performance is examined in this paper. Activated carbon remains popular due to its high surface area and low cost, but improvements in CNTs and graphene provide enhanced conductivity and structural adaptability, increasing energy and power density. It also examines the creation of carbon composites, which combine the benefits of carbon and other materials to improve supercapacitor qualities. The main factors influencing supercapacitor performance are discussed, focusing on surface modification and nanotechnology, including electrode design, pore structure, and electrolyte compatibility. Recent study findings emphasize the relevance of sustainable synthesis processes and the materials' scalability for commercial applications. The analysis continues by identifying potential prospects in carbon-based supercapacitor research, including the incorporation of environmentally friendly material production methods and the improvement of cyclic stability for long-term use in energy storage devices. This analysis provides a solid foundation for future advancements in high-performance supercapacitor technology.

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DOI: 10.3897/j.moem.11.2.163141

Authors: Vladimir G. Kostishyn, Alex V. Trukhanov, Albert A. Alekseev, Sergey V. Scherbakov, Igor M. Isaev, Andrei Yu. Mironovich, Georgy A. Skorlupin, Maksim A. Sysoev, Georgy M. Tokin

Abstract: Hexagonal anisotropic strontium ferrite has found wide application in the fabrication of permanent magnets, active media of UHF electronic devices, and photonics. The performance of hexagonal strontium ferrites depends largely on the synthesis technology. Anisotropic SrFe12O19 samples have been for the first time synthesized using radiation-thermal sintering (RTS) in a fast electron beam from an electron accelerator. The RTS temperature was varied between 1200 and 1400 °C, and the process time, from 10 to 90 min. The phase composition and lattice parameters of the samples have been monitored using X-ray diffraction and Mössbauer spectroscopy. The X-ray spectra have been recorded with a DRON-8 diffractometer in CoKα1 radiation, and the Mössbauer spectra, using an MS1104E spectrometer with a constant acceleration at room temperature, the radiation source being Со57 in a chromium matrix. The density of the specimens has been studied in accordance with Archimedes’ law on a UW620H electronic balance with a density measurement attachment. The X-ray diffraction and Mössbauer spectroscopy data show that the samples are single-phase and have the P63/mmc (No. 194) space group, corresponding to the hexagonal ferrite structure. The unit cell parameters a and c and the volume V of the samples have been studied as a function of RTS temperature for the sintering time t = 30 and 60 min. Also, the unit cell parameters a and c and the volume V of the samples have been studied as a function of sintering time for the RTS temperature T = 1300 °C. The lattice parameters a and c of the samples exhibit opposite dependences, suggesting anisotropic lattice distortion. The maximum magnetic texture degree achieved using RTS in anisotropic SrFe12O19 proves to be about 92%. It has been concluded on the basis of the Mössbauer spectroscopy data that the optimum magnetization degree of the SrFe12O19 samples is achieved for the following RTS modes (RTS temperature, °C / RTS time, min): 1300/60 and 1350/40. We show that the sintering temperature plays a considerably greater role in the RTS technology than the sintering time. Conclusion has been made that RTS can be used as an alternative technology of synthesizing polycrystalline anisotropic hexagonal SrFe12O19 ferrite. As compared to the conventional ceramic technology, RTS proves to be highly energy-efficient and cheap.

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DOI: 10.3897/j.moem.11.2.135892

Authors: Andrey N. Chibisov, Mary A. Chibisova

Abstract: The problem of creating energy-efficient quantum computers capable of performing quantum operations without errors is a significant scientific challenge in modern nanoelectronics. This type of computer can be developed using quantum transistors that contain hole qubits and are capable of performing operations on them. Hole qubits are a promising technology for quantum computers due to their strong spin-orbit interaction and the ease of control with an electric field. In this work, the influence of spin dynamics of boron impurities on the electron charge transport and electrostatic potential in a silicene structure is theoretically investigated using the noncollinear spin density method. To study spin dynamics, we calculated the dependence of the total energy change of the atomic system on the angle of rotation of the spin magnetic moments on boron atoms. It was shown that the two-dimensional system B:Si behaves as a quantum switch, allowing operations on the local distribution of charge density and electrostatic potential, thereby processing quantum information. The obtained results will be important for the technology of designing and manufacturing two-dimensional energy-efficient quantum computer.

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DOI: 10.3897/j.moem.11.2.141803

Authors: Olga F. Minchukova, Gregori Rymski, Aliaksandr L. Zhaludkevich, Oksana Romanova, Sergey Aplesnin, Lubov Udod

Abstract: The paper studies the effect of high-temperature treatment on structural and magnetic properties of the system MnZn1-xCrxSb (0 ≤ x ≤ 0.20) solid solutions obtained by solid-phase reactions with subsequent quenching. It was shown all solid solutions have a tetragonal crystal structure with P4/nmm space group, which is preserved under high-temperature treatment. The temperatures of the magnetic phase transition increase with grow substitution concentration. High-temperature treatment of the initial MnZnSb compound leads to increasing of Curie temperature and coercive force. The effect of substitution concentration on the coercive force and magnetization value has been discovered.

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DOI: 10.3897/j.moem.11.1.134921

Authors: Zahraa M. Jaafar, hamir Abdul-Jabbar Jumah, Natheer B. Mahmood

Abstract: This study presents the synthesis of LiMn0.9Fe0.1PO4 (LM9F) and its carbon-coated counterpart, LiMn0.9Fe0.1PO4 with 10% carbon (LM9F-10%C), through a straightforward solid-state method. The synthesis utilized lithium carbonate, manganese (II) acetate tetrahydrate, iron phosphate, ammonium dihydrogen phosphate, and glucose powder as the carbon source. To achieve a fine powder, a high-energy ball milling was performed at 270 rpm for 8 h, followed by calcination at 700 °C for 3 h and sintering at the same temperature for an additional 2 h, under a nitrogen atmosphere to prevent iron oxidation. Thermoanalytical techniques (TGA–DTA–DSC) were applied between 30 °C and 1000 °C to study the thermal decomposition behaviors of the precursors and pinpoint the phase formation temperature, which was identified at 416 °C. X-ray diffraction analysis verified the formation of a pure olivine orthorhombic structure, corroborated by Rietveld refinement. The morphology of the calcined powders, characterized by field emission scanning electron microscopy, showed agglomerated semi-spherical particles with an average size of 34 nm. Fourier transform infrared spectroscopy confirmed the presence of the phosphate groups integral to the olivine framework. Electrical properties measured via an LCR meter across 20 Hz to 100 kHz demonstrated that the inclusion of carbon significantly reduced impedance and improved the electrical performance of the materials.

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DOI: 10.3897/j.moem.11.1.140603

Authors: Nikolay A. Kalanda, Marta V. Yarmolich, Alexander V. Petrov, Andrey G. Yudenkov, Lyubov I. Yuzhik, Sofia S. Starukhina, Tatiana S. Ilina, Alexander S. Bykov, Dmitry A. Kiselev

Abstract: Phase transformations during crystallization of the magnetic metal-oxide compound Sr2Fe1.2Mo0.8O6-δ by the solid-phase reactions method from a mixture of simple reagents 2SrCO3 + 0.6Fe2O3 + 0.8MoO3 have been analyzed. By means of differential-thermal and thermogravimetric analyses it was found that the synthesis of strontium ferromolybdate of the Sr2Fe1.2Mo0.8O6-δ composition proceeds through a series of successive-parallel stages. In this way, when considering the dynamics of phase transformations, it has been found that the main accompanying compounds during the crystallization of the solid solution of double perovskite Sr2Fe1.2Mo0.8O6-δ are Fe2O3, SrCO3, SrMoO4 and SrFeO3. When analyzing the phase composition of the batch consisting of a mixture of initial reagents of stoichiometric composition: 2SrCO3 + 0.6Fe2O3 + 0.8MoO3, it was noted that with an increase in temperature, complex compounds SrMoO4, SrFeO3, and then Sr2Fe1.2Mo0.8O6-δ as well, appear almost simultaneously. This circumstance indicates that the compounds SrMoO4 and SrFeO3 are the structure-forming ones for the solid solution of ferromolybdate – strontium. With a subsequent increase in temperature to 1470 K, it was found that the dissolution of SrFeO3 with the formation of double perovskite Sr2Fe1.2Mo0.8O6-δ occurs faster than the dissolution of strontium molybdate SrMoO4. The results of the analysis indicate the difficult nature of the dynamics of solid-phase reactions during the formation of Sr2Fe1.2Mo0.8O6-δ.

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DOI: 10.3897/j.moem.11.1.142762

Authors: Vladzimir M. Laletin, Natallia N. Poddubnaya, Iliya S. Nabzdorov, Yurij V. Radyush, Li Jin

Abstract: The paper studies the effect of nickel ferrite addition and sintering temperature on the density, dielectric and piezoelectric characteristics of barium titanate ceramics. A density jump is detected, when with an increase in the ferrite content the density first increases and then drops sharply. Moreover, if at a sintering temperature of 1200 °C the maximum density (5.38 g/cm3) occurs at a ferrite concentration of 0.05 mol.%, then at a sintering temperature of 1300 °C the maximum density (5.62 g/cm3) shifts to the region of higher ferrite concentrations and is 0.1 mol.%. Thus, it can be stated that at a sintering temperature of 1300 °C the ferrite addition in an amount of 0.1 mol.% acts as a sintering activator. X-ray phase analysis showed that in alloyed barium titanate the tetragonal splitting of lines is expressed more strongly, and the calculated lattice parameters a and c differ significantly from the parameters of pure barium titanate. The addition of 0.1 mol.% ferrite lowers the Curie temperature of the phase transition from the cubic phase to the tetragonal phase from 117 to 108.5 °C. Activation of the sintering process with the addition of ferrite up to ~0.1 mol.% makes it possible to reduce the sintering temperature to 1300 °C and obtain ceramics with high functional characteristics. Relative density is 93%, specific resistance is ~1010 Ohm·m, permittivity is 1500, piezoelectric modulus d31 is 85 pC/N, electromechanical coupling coefficient is 0.37.

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DOI: 10.3897/j.moem.11.1.143630

Authors: Maxim V. Silibin, Dmitry A. Kiselev, Sergey I. Latushka, Dmitry V. Zhaludkevich, Alexander V. Mosunov, Dmitry V. Karpinsky

Abstract: Solid solutions of the 0.7BiFeO3–0.3Ba1-xSrxTiO3 system with compositions in the vicinity of the rhombohedral-cubic morphotropic phase boundary (x ≤ 0.3) have been synthesized via solid state reactions. The crystal structure and morphology of the solid solutions have been studied using X-ray diffraction, scanning electron microscopy and Raman spectroscopy, and the chemical composition has been studied using energy dispersive X-ray spectroscopy. The dielectric properties of the compositions have been studied using impedance spectroscopy as a function of the concentration of strontium ions over a wide range of temperatures and frequencies. The structure of the solid solutions with x ≤ 0.3 contains coexisting rhombohedral and cubic phases, strontium ion substitution leading to higher cubic phase volume fraction. The x = 0 composition contains almost equal parts of coexisting phases, whereas the x > 0.25 solid solutions have single-phase cubic structures. The concentration-related changes in the phase structure of the solid solutions lead to a decrease in the lattice parameters of the coexisting phases and a nonmonotonic decrease in the electrical conductivity and the dielectric permeability of the compositions. The experimental data provide insight into specific changes of the structure and phase composition of the solid solutions in the vicinity of the rhombohedral-cubic morphotropic phase boundary and deliver better understanding of the relationship between the observed structural changes and the electrical properties of the compositions.

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DOI: 10.3897/j.moem.11.1.136072

Authors: Saadi Berri

Abstract: In the current investigation, we have implemented first-principles calculations to examine the structural, elastic, electrical and optical characteristics of Cs2ABH6 (AB = AlGa, AlIn, AlTl, NaAl, NaGa, NaIn and TlIn). All of the calculations were performed out using first-principles density functional theory (DFT). The space group Fm-3m (225) has been used. The computed values of lattice parameters are Cs2AlGaH6: 0.8739 nm, Cs2AlInH6: 0.8923 nm, Cs2AlTlH6: 0.8953 nm, Cs2NaAlH6: 0.8669 nm, Cs2NaGaH6: 0.8688 nm, Cs2NaInH6: 0.8960 nm, Cs2TlGaH6: 0.8938 nm and Cs2TlInH6: 0.9258 nm and also it is observed that the volume and density are inversely associated with each other. In addition, the computed band-gap values for Cs2AlInH6, Cs2AlTlH6, Cs2NaAlH6, Cs2NaGaH6, Cs2NaInH6, Cs2TlGaH6 and Cs2TlInH6 and Cs2YAuCl6 are 1.21, 1.66, 2.58, 1.32, 1.42, 0.94 and 0.91 eV, respectively, which demonstrates the indirect semiconducting nature. Between 0 and 20 eV, optical spectra calculations are made, taking into account the real and imaginary parts of the dielectric function e(?), reflectivity R (?), index of refraction n (?), coefficients of extinction k (?) and absorption a(?). The dielectric function is wide close to the ultraviolet districts (3.10–4.13 eV). The extinction coefficient of the Cs2ABH6 has the ability to worn for implements like Bragg’s reflectors, optical and optoelectronic equipments. The optical parameters of Cs2ABH6 disclose that our working constructions have an elevated dielectric constant, with a greatest absorption in the visible range holding out over 2.45·105 cm-1. All three compounds fulfil the Born stability condition. The gravimetric hydrogen storage capacities of Cs2AlInH6, Cs2AlTlH6, Cs2NaAlH6, Cs2NaGaH6, Cs2NaInH6, Cs2TlGaH6 and Cs2TlInH6 compounds are 1.64, 1.20, 1.88, 1.66, 1.48, 1.02, 1.11 and 1.20 wt.%, respectively. Cs2ABH6 crystals are dynamically stable.

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DOI: 10.3897/j.moem.11.1.142461

Authors: Alexander V. Solnyshkin, Nikita V. Vostrov, Sergey I. Gudkov

Abstract: The paper studies the processes of spontaneous polarization switching in PVDF and P(VDF-TrFE) polymer films produced by 4D printing. The samples were synthesized by the direct ink writing technology. It was found that polarization reversal in PVDF samples is not observed in alternating fields less than 70 MV/m, and in P(VDF-TrFE) samples – in fields less than 35 MV/m. This phenomenon is associated, firstly, with the large mass of the objects being repolarized, which is determined by the mass of the entire polymer chain, and, secondly, with a strong dipole-dipole interaction between adjacent polymer chains of the crystalline phase of the polymer. An increase in the electric field above the specified values leads to a sharp increase in the residual polarization values and the appearance of saturated dielectric hysteresis loops. The coercive field of the P(VDF-TrFE) copolymer films is two times smaller than the corresponding value for PVDF films (38 and 80 MV/m, respectively). At the same time, the residual polarization value for the copolymer films is slightly lower than for PVDF films (30 and 35 μC/m2, respectively). The hysteresis loops were modeled according to the Preisach model. This model is based on the assumption that all lamellar crystals in the polymer have the same spontaneous polarization, each crystal has its own value of the coercive field and a rectangular dielectric hysteresis loop. The simulation showed that the average coercive field of the lamellar crystals of the PVDF polymer film is 91 MV/m, and for the P(VDF-TrFE) copolymer sample – 46 MV/m. The dispersion characterizing the distributions of the coercive and internal fields has a value of 16 MV/m for the PVDF polymer and 14 MV/m for the P(VDF-TrFE) copolymer.

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DOI: 10.3897/j.moem.11.1.133978

Authors: Oday A.H. Hassoon, Odai N.S. Salman, Vladislav N. Mironyuk, Mikhail V. Pozharov, Tatiana Ya. Karatyshova, Andrey M. Zacharevich, Evgeny G. Glukhovskoy

Abstract: The paper shows the possibility of producing photosensitive structures using physical methods without the use of chemical synthesis and vacuum techniques. Suspensions of CdSe nanoparticles were produced by pulsed laser ablation in a liquid medium (chloroform), and layers of semiconductor material (CdSe) and conductive layers (carbon nanotubes) were formed at the gas-liquid interface and transferred to solid substrates by the Langmuir–Schaeffer method. The size of CdSe nanoparticles in the layers ranged from 60 nm to 200 nm, and the bandgap was 2.3 eV. Multilayer film structures consisting of a layer based on synthesized CdSe nanoparticles and a layer of conductive carbon nanotubes, that demonstrated photosensitivity in the optical region, were obtained. The value of current density under lighting at 1 V and –1 V equals 1.25 mA/cm2 and –1.35 mA/cm2, respectively. The maximum ratio of the illumination current density to the dark current value was 13.5 times (at a voltage of 1 V).

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DOI: 10.3897/j.moem.10.4.142799

Authors: Irina V. Zaporotskova, Sergey V. Boroznin, Natalia P. Boroznina, Evgeniy S. Dryuchkov, Kseniya Yu. Verevkina, Yulia V. Butenko, Pavel A. Zaporotskov, Lev V. Kozhitov, Alena V. Popkova, Aleksandr D. Grigoriev

Abstract: The use of semiconductor nanomaterials is currently considered to be one of the most promising device optimization methods since those materials allow controlling the electronic properties and possess high mechanical and thermal strength, providing for long device service life without the necessity of replacement or seeking new solutions. The parameters of the electronic and energy structure of new semiconductor nanomaterials based on carbon nanotubes containing substitution atoms have been studied. The test carbon nanotubes contained specific substitution atom concentrations (15, 25 and 50%). A relationship has been drawn between the band gap, conductivity and optical properties of the materials. Data on the band gap and conductivity as functions of substituting nitrogen atom concentration and tube diameter have been reported. The experimental band gap data suggest that the nanotubes in question are narrow-gap semiconductors. One can also conclude that a new semiconductor material has been synthesized on the basis of carbon nanotubes with substitution nitrogen atoms since the test tubes exhibit a redistribution of electron density towards the nitrogen atoms and positive charge localization in the vicinity of the carbon atoms. The results are of utmost importance for the design and fabrication of components and units for nanoelectronics and microsystems: our theoretical study has confirmed the possibility to control the refraction index and conductivity of media by implementing a carbon-for-nitrogen substitution reaction to various concentrations. Thus, a new electronics material has been studied, i.e., carbon nanotubes modified by substitution of nitrogen atoms.

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DOI: 10.3897/j.moem.10.4.140641

Authors: Yuri Yu. Hervieu, Michael Yu. Yesin, Alexander S. Deryabin, Alexey V. Kolesnikov, Alexander I. Nikiforov

Abstract: The dynamics of monoatomic steps on the Si(100) vicinal surface during molecular beam epitaxy (MBE) growth and annealing is studied based on the analysis of reflection high-energy electron diffraction intensity variations. During growth, the initially equally spaced A- and B-steps are getting closer: the width of the A-terraces decreases to a certain minimum value, which increases with increasing growth temperature. The number of Si monolayers deposited until the minimum distance between the A- and B steps is reached increases monotonically with increasing temperature. After interrupting the Si deposition flux (during annealing) the width of the A-terrace gradually increases to the initial value. The time of such relaxation to the initial configuration of the steps decreases with increasing temperature and increasing miscut angle. The observed behavior of the steps during annealing is in good agreement with the available theoretical models of the step dynamics and is explained by the presence of an exchange flux of Si atoms between the A- and B-steps due to the elastic interaction of the steps caused by the anisotropy of the elastic stress tensor on the reconstructed Si(100) surface. However, the available models fail to explain the experimentally observed monotonically increasing temperature dependence of the number of Si monolayers deposited until the steps approach each other during growth, which indicates the need to modify the model of incorporation of Si adatoms into steps in the case of high temperatures.

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DOI: 10.3897/j.moem.10.4.142174

Authors: Aleksandr M. Kislyuk, Mikhail D. Malinkovich, Tatiana S. Ilina, Ilya V. Kubasov, Dmitry A. Kiselev, Andrei V. Turutin, Vladimir P. Ivanov, Alexander A. Temirov, Viktor V. Kuts, Evelina E. Maksumova

Abstract: Charged domain walls (CDWs) in ferroelectric materials are of interest from both fundamental and applied perspectives due to their unique electrophysical properties, which differ significantly from those of the bulk material. Until recently, research efforts primarily focused on studying these properties, while less attention was given to the finite-thickness regions of CDWs with heterogeneous electrical conductivity. This study proposes a model describing the charge carrier distribution within the conductive region of CDWs. The dependencies of charge carrier concentration and mobility on the distance from the CDW were determined. An analytical expression for current-voltage characteristics, measurable by conductive atomic force microscopy (c-AFM), was also proposed. The model has been experimentally validated using AFM methods. In particular, the Debye screening length of the electric field of head-to-head (H–H) CDWs by free charge carriers in strongly reduced LiNbO3 crystals was found to be 90±10 nm. Additionally, the values of mobility and concentration of polarons forming the conductive H–H CDW were determined. The bound polaron concentration in this region is estimated to be approximately 30 times greater than in the monodomain region, reaching ≈3.8·1017 cm-3.

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DOI: 10.3897/j.moem.10.4.136067

Authors: Shikhgasan Ramazanov, Gaji Gajiev, Daud Selimov, Sadrudin Gadzhimuradov, Sagim Suleymanov, Ştefan Ţălu, Robert S. Matos, Henrique D. da Fonseca Filho

Abstract: The structure BiFeO3/TiO2–NTs (BFOT) obtained using the atomic layer deposition. During the Anatase/Rutile phase transformation; there is a redistribution of Fe/Ti atoms, resulting in the formation of local inhomogeneities and charge trapping centres. Studies of the resistive switching effect showed nonlinear current-voltage characteristics. The negative differential resistance probably arises from the oxide dielectric layer of BFO, thin regions of which participate in the tunneling process. The BFOT surface exhibits topographic variations with spatial patterns that conform to normality, and the distribution of topographic heights displays a quasi-normal behavior. The self-affine attributes of the BFOT film are validated by the exponential reduction in autocorrelation functions, and the Minkowski functionals underscore the intricate and irregular nature of the film's topographic patterns.

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DOI: 10.3897/j.moem.10.4.144317

Authors: Sergei A. Ponomarev, Dmitry I. Rogilo, Konstantin E. Zakhozhev, Dmitry A. Nasimov, Nina N. Kurus, Anton K. Gutakovskii, Konstantin A. Kokh, Alexander G. Milekhin, Dmitry V. Sheglov, Alexander V. Latyshev

Abstract: Using in situ reflection electron microscopy we have presented latest studies of Si(111) and Bi2Se3(0001) surface processes during sublimation, homo- and heteroepitaxial growth of layered metal chalcogenides. A structural kinetic diagram of interaction between a selenium molecular beam and Si(111) surface has been demonstrated. We have shown congruent sublimation caused by annealing of Bi2Se3(0001) substrates in a selenium flux, visualized and described layer by layer homoepitaxial Bi2Se3 growth. We have presented techniques of layered SnSe2 and In2Se3 growth on Si(111) and Bi2Se3(0001) surfaces and shown that heteroepitaxial growth starts with the 2D islands formation. The nucleation and growth of an impurity-induced phase in the form of 0.4 nm high 2D islands during high-temperature submonolayer indium deposition on Bi2Se3(0001) under exposure to Se molecular beam has been demonstrated.

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DOI: 10.3897/j.moem.10.4.143751

Authors: Dmitry A. Belorusov, Evgeniy I. Goldman, Galina V. Chucheva, Mikhail S. Afanasyev, Vladimir A. Pilipenko, Alina V. Semchenko

Abstract: The performance of FeRAM non-volatile cells including those on ferroelectric insulating layers requires full-scale development of the field effect at the semiconductor–dielectric interface. The recharging of electron traps concentrated in the buffer layer between the insulator and the wafer impedes the development of the field effect at the interface. A Si wafer has been hydrogen-saturated for suppressing the activity of electron traps in the buffer layer at the ferroelectric–silicon contact. The reference specimen has been another similar wafer not exposed to H2. High-frequency C–V curves of the metal–dielectric–semiconductor structures with Ba0.8Sr0.2TiO3 insulating layers deposited on both wafers have been measured. The capacities of the test specimens have proven to be low sensitive to hydrogen saturation of the wafers. This is accounted for by long-term heating of the silicon wafers at 500–600 °C during ferroelectric deposition. It has been proposed to implant large organic cations into the wafers in order to reduce the concentration of electron traps in the Ba0.8Sr0.2TiO3–Si buffer layers. Those organic cations can be 2–phenylethyl ammonium iodide, 4-chlorophenylethyl ammonium iodide and 4-fluorophenylethyl ammonium iodide which showed good results at passivation of high-performance metal–halogenide perovskite solar cells.

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DOI: 10.3897/j.moem.10.4.142304

Authors: Ilya V. Kubasov, Andrei V. Turutin, Aleksandr A. Temirov, Viktor V. Kuts, Evelina E. Maksumova, Aleksandr M. Kislyuk, Mikhail D. Malinkovich

Abstract: This study examines the bending dynamics of cantilevered single-crystalline bimorphs made from bidomain LiNbO3 (BLN), emphasizing the interaction between bending resonances, antiresonances, and torsional vibrations. Combining theoretical modeling and experimental validation, we demonstrate that a 1D analytical model, based on classical beam theory, surpasses FEM modeling in predicting bending resonances, particularly in the low-frequency range. The analytical model provides precise positioning of resonant frequencies, enabling the strategic alignment of torsional resonances with bending antiresonances, as confirmed experimentally. Our findings underscore the high predictability of BLN-based bimorphs, allowing accurate descriptions of their behavior at bending resonances, antiresonances, and piezoelectrically passive torsional resonances. Unlike glued actuators made of lead-based ceramics, BLN bimorphs offer superior thermal stability, long-term reliability, and predictable performance. These properties, combined with the availability of commercially produced LN crystals, position BLN-based bimorphs as ideal candidates for MEMS applications, enabling advanced sensing and actuation solutions with reduced reliance on complex feedback loops.

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DOI: 10.3897/j.moem.10.3.140714

Authors: Ulyana M. Matveyenka, Elena A. Skryleva, Elena N. Abramova, Roman Yu. Kozlov, Pavel V. Pavlov, Ivan V. Sidelnikov, Olesya S. Pavlova

Abstract: Rapid development of III–V semiconductor device technologies and broadening of device applications are hindered by the high density of surface states produced in those materials by intrinsic complex oxides and surface contaminations. Surface oxides acting as non-radiating recombination centers produce a number of surface levels in the band gap. Oxidation mechanisms depend on the chemical composition of a specific III–V semiconductor compound because surface reactivities differ between materials. The effect of chemical bond polarity on surface oxidation processes in single crystal III–V semiconductor wafers is currently an important research topic. In this work, surface-sensitive XPS method has been used for studying oxidation regularities in GaAs, InAs, GaSb and InSb single crystals undergoing natural atmospheric oxidation and subjected chemical-mechanical polishing. A method of assessing oxidation levels based on chemical shifts of XPS spectral features has been developed. Oxidation level has been shown to depend on chemical bond ionicity degree, the latter being evaluated using the Sanderson and Phillips models. A decrease in surface oxidation level with an increase in bond ionicity degree has been observed for (110) single crystal wafer cleavage surfaces and for (100) single crystal wafer surfaces after single crystal slicing and chemical-mechanical polishing. We show that surface oxidation level increases in the InAs–GaAs–InSb–GaSb sequence, from arsenides to antimonides.

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DOI: 10.3897/j.moem.10.3.134474

Authors: Valery N. Mishchanka

Abstract: Graphene, which has a high mobility of charge carriers, which exceeds the mobility of charge carriers for all known materials, is currently considered as one of the most promising materials for the creation of new semiconductor devices. The results of modeling of electron scattering rates are presented for the acoustic and optical phonons in a single layer of graphene without a substrate for small values of energy, which do not exceed 1 eV. When modeling these rates, variants of both emission and absorption of phonons are considered. The obtained dependences of the charge carrier scattering rates will allow us to study the main characteristics of charge carrier transport in semiconductor structures containing graphene layers by modeling using the Monte Carlo method. Characteristics and parameters of graphene can be used to create new heterostructure devices with improved output characteristics.

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DOI: 10.3897/j.moem.10.3.140627

Authors: Nataliya A. Verezub, Anatoly I. Prostomolotov

Abstract: Mathematical simulation results for inert gas (argon) dynamics in the rarefied atmosphere of Redmet-10 Cz single crystal silicon growth furnace chamber have been reported. Gas flows in cold (room temperature) and hot (growth process) chambers have been analyzed. Convective gas flows have been considered for two growth chamber gas supply options: basic supply, i.e., through the top central inlet hole only, and combined, i.e., with additional gas supply through the lateral inlet hole. Gas outlet is through the growth chamber bottom outlet hole for both options. For the cold chamber option, forced convection has been studied using the incompressible ideal gas model. For hot chamber, both the nonisothermal compressible ideal gas model and the weakly compressible gas model in the Boussinesq approximation have been used for studying the vortex structure produced by a joint action of forced and thermal-gravitational convection. The effect of different gas inlet methods on the convective transport of silicon monoxide evaporating from the free melt surface has been discussed.

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DOI: 10.3897/j.moem.10.3.140732

Authors: Vladimir A. Makagonov, Konstantin S. Gabriel’s, Yuri E. Kalinin, Artem Yu. Lopatin, Ludmila A. Bliznyuk, Alexander K. Fedotov

Abstract: A method of measuring the thermovoltaic effect in heterogeneous media with gradient doping impurity distributions producing gradient carrier distributions has been proposed. Iron doped zinc oxide specimens have been produced using ion beam sputtering on thin foil tantalum substrates for thermovoltaic effect measurements, glass-ceramic substrates for Hall measurements and silicon substrates for structural study. The doping impurity concentration хFe in the specimens has been varied from 0.34 to 4.18 at.%. X-ray phase analysis has shown that all the specimens have a hexagonal zinc oxide crystal structure. The films have preferential [002] orientation. The carrier concentration in the experimental specimen layers according Hall data obtained on an ECOPIA 5500 measurement system in a 0.5 T DC magnetic field has varied in the 1016–1020 cm-3 range. The specimens have an n-type conductivity. Thermovoltaic measurements have been carried out for two-layered iron doped zinc oxide specimens with different carrier and iron doping impurity concentrations using the method proposed. The maximum thermovoltaic response (U ~ 80 μV) has been observed in the two-layered thin-film specimen with the carrier concentration difference between the layers (Δn ≈ 2∙103 cm-3). The observed saturation of the thermovoltaic response has been attributed to the establishment of dynamic equilibrium between carrier diffusion from the high carrier concentration layer to the low carrier concentration layer and carrier drift due to internal electric field.

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DOI: 10.3897/j.moem.10.3.131526

Authors: Utkir Uljayev, Shahnozakhon Muminova, Kamoliddin Mehmonov, Ishmumin Yadgarov, Abror Ulukmuradov

Abstract: Boron-adsorbing carbon nanotubes receive considerable attention in materials science due to their unique properties and potential applications. In particular, boron-adsorbing double-walled carbon nanotubes (DWNTs) exhibit a wide range of tunable electronic and optoelectronic properties. This study explores the influence of boron atoms on metallic (5,5@10,10) and semiconducting (8,0@17,0) DWNTs. We examine alterations in partial charge depending on the quantity of boron atoms adsorbed and affixed to the DWNT surface across temperatures from 300 K to 900 K. The results show that in both DWNTs, with the increase of energy corresponding to the temperature, the adsorption index of boron atoms (adsorbed to the first layer of DWNT) and the positive partial charge increase. Specifically, the maximum partial charge of DWNT(8,0)@(17,0) and DWNT(5,5)@(10,10) is 1.94e and 1.30e (at 300 K), 4.87e and 3.66e (at 600 K), 6.97e and 6.16e (at 900 K). Increasing boron concentration leads to heightened positive partial charge of DWNTs. This, in turn, affects the conductivity of the nanotube.

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DOI: 10.3897/j.moem.10.3.135986

Authors: Andrey N. Chibisov, Daria M. Smotrova, Mary A. Chibisova, Aleksandr S. Fedorov

Abstract: The design of two-dimensional superatomic materials, which form their atomic structures through covalently bonded clusters with variable chemical compositions, will enable the development of new materials with promised electronic properties that are beneficial for modern nanoelectronics. This paper presents ab initio calculations of the atomic and electronic structures of both bulk and 2D Re6Se8Cl2. The calculations were carried out using density functional theory, incorporating noncollinear spin density and the pseudopotential method. The results include data on the atomic structure, band gap value, formation energy of the Re6Se8Cl2 2D layer, and the redistribution of atomic charges within the structures. The differences in effective masses for electrons and holes in the two-dimensional and bulk Re6Se8Cl2 materials are demonstrated, along with an explanation of how these differences impact their transport properties. The findings are expected to be of great significance for the design, synthesis, and implementation of new two-dimensional superatomic materials with controlled properties in modern nanoelectronics.

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DOI: 10.3897/j.moem.10.2.131698

Authors: Nikolai A. Sobolev

Abstract: The review looks at the main trends in global energy production and consumption over the last half century, based on P.L. Kapitza’s 1975 analysis using a unified approach based on the Umov–Poynting vector. Such aspects of the problem as the impact of energy consumption on gross national product per capita, reasons for different approaches of countries to the transition to renewable energy sources, existing sources of energy, global distribution of its production and consumption, features and prospects of different energy technologies, as well as technologies to reduce energy consumption are touched upon. Thus, since 1975, the price of one kilowatt-hour of "solar" electricity has fallen by orders of magnitude and this technology has moved to the forefront, while fusion still remains the "energy of the future" and coal continues to hold its position in the market. Somewhat unexpectedly, electronics and telecommunications have become a major consumer of energy, urging a shift from von Neumann architecture to neuromorphic technology in computers and the development of femto and attowatt optoelectronics. And a totally unforeseen energy consumer has been cryptocurrency mining. On the other hand, the harvesting of dissipated energy in a variety of ways is seen as an environmentally friendly alternative to the use of batteries in low and ultra-low-power devices.

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DOI: 10.3897/j.moem.10.2.129169

Authors: Zahraa M. Jaafar, Thamir Abdul-Jabbar Jumah, Natheer B. Mahmood

Abstract: In this study, the synthesis, structural characterization, and electrical property analysis of LiMn0.8Fe0.2PO4 (LM8F) and its carbon-composite variant (LM8F-10%C) as potential cathode materials for solid-state lithium batteries were reported. Employing high-energy ball milling (HEBM) followed by calcination, LM8F was synthesized using ammonium dihydrogen phosphate, lithium carbonate, manganese(II) acetate tetra-hydrate, and iron(III) phosphate as precursors. The introduction of glucose as a carbon source aimed at the formation of a carbon-coated composite to enhance the electrical conductivity of the material. Structural and morphological characteristics of the synthesized materials were elucidated through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FeSEM). The XRD results confirmed the olivine and orthorhombic structure of the synthesized material, highlighting its suitability for use as a cathode in solid-state lithium batteries. Electrical properties were assessed using an LCR meter to examine the impact of carbon coating on electrochemical performance. The findings demonstrated that the inclusion of carbon significantly improved the electrical conductivity, potentially leading to enhanced battery performance. This work contributes to the development of high-performance cathode materials for solid-state lithium batteries, paving the way for future advancements in energy storage technologies.

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DOI: 10.3897/j.moem.10.2.124089

Authors: Fedor A. Fedulov, Dmitrii V. Savelev, Yuri K. Fetisov

Abstract: Nowadays, one of the promising ways for the development of computing systems with high performance and low energy consumption is the creation of artificial synaptic devices that imitate the functions of biological synapses. Such devices have a significant potential for effectively solving problems of pattern recognition, classification, control, and the treatment of diseases of the nervous system. The work demonstrates the imitation of synaptic behavior in a composite multiferroic heterostructure based on the piezoceramics of lead zirconate titanate (PZT) and the amorphous magnetic alloy Metglas. The characteristics of the heterostructure were measured by resonant excitation of the magnetoelectric (ME) effect and applying electric field pulses of various amplitudes and polarities. The ME coefficient αE was considered as a synaptic weight, and the output electrical voltage of the heterostructure as a postsynaptic potential. The study demonstrates the possibility of simulating long-term potentiation (LTP) and depression (LTD) in the ME heterostructure, as well as spike-timing-dependent plasticity (STDP). This work shows promise for creating neuromorphic computing systems based on multiferroic composite heterostructures.

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DOI: 10.3897/j.moem.10.127996

Authors: Valery R. Sobol, Maxim V. Silibin, Dmitry V. Karpinsky

Abstract: Dispersion relations for a transverse electromagnetic wave in a hypothetical medium having a low crystalline symmetry and double anisotropy are formulated phenomenological based on the general concepts of Maxwell's equations. Formalism for electrical and magnetic ordering of a medium is represented by tensor coefficients of the second rank in a general coordinate system corresponding to an external problem of incidence, reflection and refraction of a transverse wave at the interface. Based on the obtained dispersion law, the Snell law of refraction for the wave vector is displayed, as well as, some special cases for a section of a wave surface and a ray surface in the plane of incidence. Following Fresnel approach as usual, two characteristic types of linear polarization of an electric induction vector of a propagating wave are considered for a wave entering a double anisotropic medium at an arbitrary angle to the interface. Based on a character of a cross-section of a wave surface and of a ray surface for the plane of incidence, the degree of influence of anisotropy on a propagating field is discussed in terms of external/internal conic refraction of ordinary/extraordinary waves in a transparent medium. Following to initially general form of the permittivity ε^ and the magnetic permeability μ^ tensors some particular cases of a more favorable choice of coordinate system are analyzed to decrease a number of non-zero components in mentioned tensors, as well as to decrease in the number of elements in vector relations.

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DOI: 10.3897/j.moem.10.2.129762

Authors: Vladimir M. Kravchenko, Victoria V. Malyutina-Bronskaya, Hanna S. Kuzmitskaya, Anton V. Nestsiaronak

Abstract: This paper presents the results of obtaining and studying the electrical and optical characteristics of an optically transparent highly conductive Ni/Cu/Ti/ITO contact in order to reduce electrical resistance losses on the front side of the silicon solar cell. The topology of the contact metallization is a square 50 × 50 mm2 with an interdigitated electrode structure. A Ni/Cu/Ti contact metallization formed on ITO layer reduces the surface resistance by more than 60 times. It has been shown that the use of a Ni/Cu/Ti contact with a finger thickness of at least 1.5 μm and a width of 17 μm was formed is a good alternative to traditional contacts for silicon solar cells based on silver paste.

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DOI: 10.3897/j.moem.10.2.126396

Authors: Dmitriy G. Muratov, Lev V. Kozhitov, Irina V. Zaporotskova, Alena V. Popkova, Vladimir V. Sleptsov, Artem V. Zorin

Abstract: Various types of metal-organic frameworks (MOF) and their structural parameters have been reviewed and their classification has been presented. Most widely used synthesis methods and approaches for MOF and composites on their basis have been discussed. MOF structure is a regular 3D lattice formed by organic linkers and metallic clusters. It has been shown for an example of literary data on MOF synthesis and structural studies that the types of bonds and metals can strongly affect the spatial structure and dimensions of MOF crystals: they can have nano-, micro- and meso-dimensions, be dense or porous, bulk or layered. This variety of structural parameters determines the wide range of their properties and potential applications. Prospects and methods of controlling the shapes of the crystals, their size and spatial bonds between organic components and metal ions have been reviewed. Major attention has been paid to zeolite-like frameworks (ZIF) as the most promising ones from the viewpoint of structure, synthesis and electrochemical current source applications. Discussion has touched on possible modifications and methods of controlling the properties of those MOFs and composites on their basis and introduction of impurities, including those having magnetic properties. Possible synthesis options of complex composites through controlled MOF pyrolysis have been presented, for either small-batch or scalable processes. The effect of heat treatment conditions on the final properties and electrochemical applications of those materials has been demonstrated. ZIF-67 structured MOF doping with one more metal has been presented as variant of modifying the properties of MOF and composites on their basis. For example, the Authors have implemented cobalt MOF synthesis wherein cobalt is partially substituted for manganese at the synthesis stage. Furthermore, a simple water solution co-deposition synthesis technique has been modified with ultrasonication thus reducing the time consumption of the process. Electrochemical studies have shown that the unit electrochemical capacity of pyrolyzed MOF electrodes with partial cobalt substitution for manganese is appreciably higher as compared to the manganese-free materials. The unit capacity and energy density increase with manganese content in the MOF. MOF manganese doping delivers a considerable improvement in the electrochemical parameters of the electrode materials for hybrid supercapacitors on their basis (from 100 to 298 F/g at 0.25 A/g current density). The results suggest that cobalt substitution for manganese is an effective method of improving the electrochemical parameters of MOFs. It has been demonstrated that the development of new approaches to the design of MOF based composite materials and the study of the physicochemical regularities of their interaction with various carriers is an important task.

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DOI: 10.3897/j.moem.10.1.127026

Authors: Irina S. Voronina, Elizaveta E. Dunaeva, Liudmila I. Ivleva, Liudmila D. Iskhakova, Alexandr G. Papashvili, Maxim E. Doroshenko

Abstract: High-temperature diffusion doping has been used for the introduction of active cobalt ions in calcium orthovanadate Ca3(VO4)2 single crystals (CVO). The test samples have been produced from nominally pure Cz CVO single crystals. High-temperature diffusion conditions have been optimized for the obtaining of doped optical quality single crystals in open or closed zone annealing. The diffusion coefficients of cobalt ions have been calculated for different conditions. Temperature regime, process time, diffusant type were defined. The samples have been annealed at 1150–1300 °C for 24–48 h with Co3O4, Ca10Co0.5(VO4)7 and Ca3(VO4)2 : 2 wt.% Co3O4 as diffusants. The diffusion direction has been parallel or perpendicular to the optical axis of the CVO crystal. The diffusion coefficients have been calculated to be in the range of 2.09 · 10-8 – 1.58 · 10-7 cm2/s. The diffusion activation energies have been determined to be 2.58 ± 0.5 and 2.63 ± 0.5 eV for the [001] and [100] directions, respectively. The maximum cobalt concentration in the doped CVO crystals has been found to be 2 · 1020 cm-3. The absorption spectrum of the diffusion doped Ca3(VO4)2 : Co samples has exhibited absorption bands typical of the Co2+ and Co3+ ions. It has been shown that the intensity ratio between the characteristic absorption bands varies depending on crystal obtaining technique. The optical anisotropy of the crystal increases with dopant concentration.

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DOI: 10.3897/j.moem.10.1.116991

Authors: Bini P. Pathrose, V. P. N. Nampoori, A. Mujeeb

Abstract: The thermal diffusivity calculations of 4-[(4-aminophenyl)-(4-imino-1-cyclohexa-2,5-dienylidene) methyl] aniline hydrochloride were made for four distinct concentrations of dye dissolved in three solvents. The number of dye aggregates at higher concentrations produce more random collisions. Because of this, heat diffusion will be slower and a reduced thermal diffusivity value was observed. Due to the increased number of dye molecules, cluster formation can also occur at higher concentrations which further reduces the thermal transport through the media. Fourier-transform infrared spectroscopy (FTIR) showed the vibrational bonds of the dye in the three solvents. The dye dissolved in acetone showed higher diffusivity as compared to the other two solvents. Our studies revealed that thermal diffusivity of the dye under study is strongly solvent dependent as well as concentration dependent. The dye under study could be effectively used as insulators or heat sinks with proper choice of concentration and solvent.

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DOI: 10.3897/j.moem.10.1.113631

Authors: B. M. Shilpa, Sathisha K. Shet

Abstract: Micro-electromechanical system-based semiconductor sensor systems typically need a reliable on-chip analog readout circuit to identify and process changes in physical properties. To improve the mobility, robustness, reliability and performance (in terms of power consumption and speed) of the sensor system, the remaining parts of the post-processing logic, such as the digital data processor (or part of it), can also integrated into the chip. Cost and integration are always important considerations in both analog and digital designs, but they become even more important; the subsystem of data processing must be squeezed into a very small space near the structure of the micro-electromechanical system (MEMS) sensor. The paper introduces a new Buffalo-based register-transfer level (BRTL) method that aims to improve the efficiency and reliability of the system of digital data processing for MEMS sensor post-processing algorithm. Initially, the memcomputing system was designed with the needed functional processing elements. Then, a novel Buffalo-based register-transfer level design is modelled in the MEMS architecture. The digital data transmission process is performed to estimate the reliability of the proposed BRTL model. Finally, the performance of the proposed model can be validated.

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DOI: 10.3897/j.moem.10.1.130290

Authors: Andrey V. Telegin, Zhimba Zh. Namsaraev, Vladimir D. Bessonov, Valentin S. Teplov, Alexey V. Ognev

Abstract: Multilayered metallic nanostructures are promising for the fabrication of spin valves based on the giant magnetoresistive effect and for studies of the nature of topological magnetism, aimed at the development of new nanoscale data storage and transfer devices, e.g. those based on magnetic skyrmions. It is still an important task to develop methods of synthesis and configuration of thin-film nanostructures and control of spin textures in those nanostructures under electric and spin currents generated as a result of the spin Hall effect in external electric fields. Thin-film polycrystalline ferromagnetic / heavy metal Ru(10nm)/Co(0,8)/Ru(2), Ru(10)/Co(0,8)/Ru(2)/W(4), Pt(5)/Co(0,8)/MgO(2)/Pt(2) and Pt(15)/Co(0,8)/MgO(2)/Pt(2) nanostructures have been synthesized using magnetron sputtering. Electric contacts and Hall structures with different conductive bridge thicknesses have been synthesized on the specimens using electron beam photolithography. Experimental vibration magnetometric data have been utilized to calculate magnetic parameters of the specimens, i.e., saturation magnetization, magnetic anisotropy energy and field and coercive force as functions of ferromagnetic and heavy metal layer types. The domain structure of the specimens has been studied using Kerr microscopy. The electrical resistivity has been simulated and the critical current and current density of the nanostructures have been assessed. We show that all the film specimens exhibit perpendicular magnetic anisotropy and can be used in the studies of current-induced phenomena and spin moment transfer processes in nanostructures.

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DOI: 10.3897/j.moem.10.1.122043

Authors: Artem S. Chislov, Mikhail A. Borik, Aleksey V. Kulebyakin, Elena E. Lomonova, Filipp O. Milovich, Valentina A. Myzina, Aleksey A. Reu, Polina A. Ryabochkina, Natalya V. Sidorova, Nataliya Yu. Tabachkova

Abstract: The phase composition, density, microhardness and fracture toughness of (ZrO2)1-x(R2O3)х crystals (where R = Y, Sm and Gd) for x = 0.02–0.04 have been compared. The crystals have been grown using directional melt crystallization in a cold crucible. The phase composition of the crystals has been studied using X-ray diffraction and Raman spectroscopy. The microhardness and fracture toughness of the crystals have been evaluated by means of indentation. At stabilizing oxide concentrations of ≥ 2.8 mol.% for Y2O3 and Gd2O3 and ≥ 3.7 mol.% for Sm2O3 the crystals have densities close to the theoretical ones and contain two tetragonal phases. At lower stabilizing oxide concentrations the crystals contain the monoclinic phase. The fracture toughness of the tetragonal crystals increases with the ionic radius of the stabilizer. The highest fracture toughness values achieved when stabilized by a specific oxide are 11.0, 13.0 and 14.3 MPa·m1/2 for the 2.8YSZ, 2.8GdSZ and 3.7SmSZ crystals, respectively. The fracture toughness proves to depend on the crystallographic orientation of the crystals. The results of this work can be used in the design and fabrication of various structural components and devices.

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DOI: 10.3897/j.moem.10.1.121618

Authors: Moses T. Njovana, Monageng Kgwadi, Sajid M. Sheikh

Abstract: This paper presents the characterisation of the three distinct materials considered to be used as a resistance-type strained-based sensor on a wearable device. Other performance parameters besides the usual linearity, sensitivity, working range, and hysteresis were also considered. These included the resistance variations caused by a changing temperature, the effects of moisture on the sensor's resistance, and the stress coefficient of resistance. These were necessitated by the nature of the operational environment of most wearable sensors, which may entail the heat introduced to the sensor due to its proximity to the human body, the moisture from perspiration and the limited amount of force that a feeble patient say, can be able to exercise on the sensor. The selected sensor had a high degree of linearity, as established using the linear regression model (R2 = 0.94), had a decent sensitivity (gauge factor = 1.7), a working range of at least 30% strain, and suffered insignificant hysteresis (6.3%). This sensor also had a moderate stress coefficient of resistance (0.11%/KPa) and was unaffected by the changes in temperature and moisture. And the best part is that it is also low-cost.

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DOI: 10.3897/j.moem.9.4.116107

Authors: Marta V. Yarmolich, Nikolay A. Kalanda, Alexander V. Petrov, Dmitry A. Kiselev, Nikolay A. Bosak

Abstract: This paper presents investigations of phase transformations during the crystallization of Sr1.5La0.5FeMoO6-δ by the solid-phase technique from a stoichiometric mixture of oxides MoO3, La2O3 and Fe2O3 and SrCO3 and precursors Sr0.5La0.5FeO3 and SrMoO4. Using XRD and thermogravimetric analyses, the influence of synthesis modes on the chemical processes occurring during the formation of double perovskite was studied. It has been established that the synthesis of lanthanum-strontium ferromolybdate in a mixture of oxides proceeds through a number of series-parallel stages. At the initial stage of interaction, the resulting lanthanum-strontium ferromolybdate is enriched with iron and its composition changes during the reaction towards an increase in the molybdenum content. As the temperature increases, the content of double perovskite increases, and the concentration of the secondary phase SrMoO4 does not disappear to zero until the synthesis temperature, which indicates that solid-phase reactions with the formation of a solid solution Sr1.5La0.5FeMoO6-δ from oxides are difficult to occur. It was determined that to minimize the influence of intermediate reaction products it is necessary to use precursors Sr0.5La0.5FeO3 and SrMoO4. Based on the results of studying the temperature dependences of the degree of phase transformations during the crystallization of double perovskite, combined heating modes were optimized. The use of optimized synthesis modes made it possible to obtain single-phase Sr1.5La0.5FeMoO6-δ powder with the superstructural ordering (82%), the Curie temperature of 450 K and a magnetization value of 40.9 A · m2 · kg-1 at T = 77 K in a magnetic field with induction B ≥ 0.86 T.

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DOI: 10.3897/j.moem.9.4.116552

Authors: Alexander A. Temirov, Ilya V. Kubasov, Andrei V. Turutin, Tatiana S. Ilina, Alexander M. Kislyuk, Dmitry A. Kiselev, Elena A. Skryleva, Nikolai A. Sobolev, Igor A. Salimon, Nikolai V. Batrameev, Mikhail D. Malinkovich, Yuri N. Parkhomenko

Abstract: Silicon-carbon films are of great interest as diamond-like materials combining unique properties, e.g. high hardness, adhesion to a wide range of materials, abrasion resistance, chemical resistance, low friction coefficient and biocompatibility. The presence of silicon in the films significantly reduces their inner mechanical stress as compared to diamond films. Currently, the films are used in industry, primarily, as solid lubricants and protective coatings. There are a large number of silicon-carbon film synthesis methods the most widely used of which are various options of chemical vapor deposition. A new silicon-carbon film synthesis technique has been suggested and tested. The technique is based on the use of high-frequency induction for obtaining plasma of silicon and carbon vapors supplied to the reaction chamber from an external source. Impurity-free silicon-carbon films containing 63–65 % carbon atoms with sp3 orbital hybridization have been synthesized on Sitall substrates. The composition, surface roughness and friction coefficient of the impurity-free silicon-carbon films synthesized using the suggested technology have been studied. The possibility of implementing resistive switching in thin silicon-carbon films in cross-bar structures with metallic electrodes has been analyzed.

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DOI: 10.3897/j.moem.9.4.116423

Authors: Mikhail G. Lavrentev, Mikhail V. Voronov, Aleksey A. Ivanov, Viktoriya P. Panchenko, Nataliya Yu. Tabachkova, Maksim K. Tapero, Ivan Yu. Yarkov

Abstract: The strength and thermoelectric properties of PbTe and Sn0.9Pb0.1Te medium-temperature polycrystalline specimens with p and n conductivity types, respectively, have been studied. The specimens have been produced using extrusion and spark plasma sintering. The strength parameters of the materials were studied using uniaxial compression at 20 to 500 °C. The structure of the materials was studied using X-ray diffraction and electron microscopy. The electrical conductivity and the Seebeck coefficient were measured simultaneously using the four-probe and differential methods. The temperature conductivity and the specific heat capacity were measured using the laser flash and differential scanning calorimetry methods. The PbTe and Sn0.9Pb0.1Te materials produced using extrusion and spark plasma sintering prove to be single-phase and have homogeneous compositions. For comparable synthesis methods, the dislocation density in the Sn0.9Pb0.1Te specimens is by an order of magnitude lower than in the PbTe ones. Study of the mechanical properties of n and p conductivity type specimens over a wide temperature range from 20 to 500 °C has shown that their deformation is plastic and has no traces of brittle fracture. For these plastic materials, the strength criterion has been accepted to be the arbitrary yield stress corresponding to the stress at a 0.2% deformation. The 20 °C yield stress of PbTe and Sn0.9Pb0.1Te is far higher for the specimens produced by extrusion. For all the test temperatures and synthesis methods the Sn0.9Pb0.1Te specimens have a higher strength than the PbTe ones. The PbTe and Sn0.9Pb0.1Te specimens produced by extrusion have better thermoelectric properties than the spark plasma sintered ones. The heat conductivity of the PbTe and Sn0.9Pb0.1Te specimens is almost the same regardless of compaction method.

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DOI: 10.3897/j.moem.9.4.116646

Authors: Aleksandr M. Kislyuk, Ilya V. Kubasov, Alexander A. Temirov, Andrei V. Turutin, Andrey S. Shportenko, Viktor V. Kuts, Mikhail D. Malinkovich

Abstract: Charged domain walls (CDWs) in ferroelectric materials raise both fundamental and practical interest due to their electrophysical properties differing from bulk ones. On a microstructure level, CDWs in ferroelectrics are 2D defects separating regions with different spontaneous polarization vector directions. Screening of electric field of the CDW's bound ionic charges by mobile carriers leads to the formation of elongated narrow channels with an elevated conductivity in initially dielectric materials. Controlling the position and inclination angle of CDW relative to the spontaneous polarization direction, one can change its conductivity over a wide range thus providing good opportunities for developing memory devices, including neuromorphic systems. This review describes the state of art in the formation and application of CDWs in single crystal uniaxial ferroelectric lithium niobate (LiNbO3, LN), as resistive and memristive switching devices. The main CDWs formation methods in single crystal and thin-film LN have been described, and modern data have been presented on the electrophysical properties and electrical conductivity control methods of CDWs. Prospects of CDWs application in resistive and memristive switching memory devices have been discussed.

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DOI: 10.3897/j.moem.9.4.115181

Authors: Mikhail S. Afanasiev, Dmitry A. Kiselev, Alexey A. Sivov, Galina V. Chucheva

Abstract: In this work, the membrane structures based on lead-free ferroelectric barium strontium titanate with composition Ba0.8Sr0.2TO3 (BSTO) were fabricated by a magnetron sputtering method. The formation of a single-phase Ba0.8Sr0.2TO3 with thickness of 300 nm sintered on Si substrate is confirmed by XRD analysis. It is shown that films without a silicon substrate exhibit ferroelectric and piezoelectric properties. The piezoelectric and ferroelectric behaviors of BSTO thin film without a silicon substrate were confirmed through a piezoelectric force microscopy and Kelvin probe force microscopy and measurements of the effective piezoelectric coefficients (d33 and d15). Images of the residual potential of polarized areas have been obtained on the membranes, which are stable over time despite the absence of a lower electrode. Additionally, a local of ferroelectric hysteresis loop has been observed. A combination of the structural and piezoelectric measurements reveals that it possible to create freestanding ferroelectric films based on Ba0.8Sr0.2TO3 system, establishing it as a promising candidate for high-performance electromechanical applications.

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DOI: 10.3897/j.moem.9.4.116620

Authors: Maxim V. Silibin, Polina A. Sklyar, Vadim D. Zhivulko, Sergey I. Latushko, Dmitry V. Zheludkevich, Dmitry V. Karpinsky

Abstract: Complex transition metal oxides are distinguished for a close interrelation between their type of crystal structure and electrical and magnetic properties, thus determining their practical importance. Bismuth ferrite based solid solutions contain simultaneously both dipole electric and magnetic ordering thus expanding their potential applications as external impact sensors. The sensitivity of these compositions to external fields is largely dependent on their structural state. 0.65BiFeO3–0.35Ba1-xSrxTiO3 solid solutions (0 ≤ x ≤ 1) the compositions of which are close to the rhombohedral/cubic morphotropic phase boundary have metastable structures and are therefore promising functional materials. The crystal structure and morphology of 0.65BiFeO3–0.35Ba1-xSrxTiO3 solid solutions has been studied using X-ray diffraction, scanning electron microscopy, Raman spectroscopy and energy dispersive X-ray spectroscopy. The chemical substitution of barium ions for strontium ones has been found to reduce the magnitude of rhombohedral distortions and decrease the unit cell parameters for all the substituted compounds. Solid solutions with x ≥ 0,25 have single-phase structure and cubic unit cells, their grain size decreasing with an increase in the concentration of the substituting ions. The results of structural studies obtained using Raman spectroscopy suggest the presence of rhombohedral distortions in the structures of all the compositions studied. The results of structural studies have allowed identifying the sequence of changes in the phase state and lattice parameter of the compounds in the vicinity of the rhombohedral/cubic morphotropic phase boundary. The concentration ranges in which the compounds have single-phase and two-phase structures have been found. The concentration stability range of the polar rhombohedral phase has been corrected on the basis of the structural data obtained using local and microscopic methods.

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DOI: 10.3897/j.moem.9.3.115403

Authors: Vitaly A. Tarala, Alexander A. Kravtsov, Sergey V. Kuznetsov, Fedor F. Malyavin, Oleg M. Chapura, Ekaterina A. Brazhko, Lev V. Kozhitov

Abstract: Optical ceramics based on YSAG : Yb : Er with the compositions {Y1.86Yb0.45Er0.09Sc0.6}[Al1.6Sc0.4]Al3O12 and {Y2.26Yb0.45Er0.09Sc0.2}[Al1.0Sc1.0]Al3O12 were fabricated by vacuum sintering from pre-synthesized nanocrystalline powders. A comparative analysis of these samples with optical ceramics of the compositions {Y2.34Yb0.45Er0.09Sc0.12}[Al1.92Sc0.08]Al3O12 and {Y0.96Yb0.45Er0.09Sc1.50}[Al1.8Sc0.2]Al3O12 was carried out. The influence of scandium cations in the dodecahedral and octahedral positions of the garnet crystal lattice on the refractive index of YSAG : Yb : Er, as well as the values of absorption coefficients, integral luminescent intensities, and lifetimes of excited states of Yb3+ (2F7/2 and 2F5/2) and Er3+ (4I15/2, 4I13/2, 4F9/2, and 4S3/2) cations was revealed in the wavelength ranges 520–700 nm and 890–1690 nm. It has been shown that by changing the concentrations of scandium cations in the dodecahedral and octahedral positions of the crystal lattice of YSAG : Yb : Er solid solutions, it is possible to purposefully change the efficiency of energy transfer from ytterbium cations to erbium cations.

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DOI: 10.3897/j.moem.9.3.115614

Authors: Mikhail A. Borik, Aleksej V. Kulebyakin, Elena E. Lomonova, Filipp O. Milovich, Valentina A. Myzina, Polina A. Ryabochkina, Natalya V. Sidorova, Nataliya Yu. Tabachkova, Artem S. Chislov

Abstract: The effect of high-temperature treatment in different media on the phase composition, microhardness and fracture toughness of (ZrO2)1-х(Sm2O3)х crystals with x = 0.02÷0.06 has been studied. The crystals have been grown using direction melt crystallization in a cold skull. The crystals have been heat treated at 1600 °C for 2 h in air and in vacuum. The phase composition of the crystals has been studied using X-ray diffraction and Raman scattering. We show that samarium cations enter the ZrO2 lattice mainly in a trivalent charge state and do not change their charge after air or vacuum annealing. The as-annealed phase composition has changed in all the test crystals except for the (ZrO2)0.94(Sm2O3)0.06 composition. After air or vacuum annealing the (ZrO2)1-x(Sm2O3)x crystals with 0.002 ≤ x ≤ 0.05 contain a monoclinic phase. The (ZrO2)0.94(Sm2O3)0.06 crystals contain two tetragonal phases (t and t´) with different tetragonality degrees. After air or vacuum annealing of the (ZrO2)0.94(Sm2O3)0.06 crystals the lattice parameters of the t and t´ phases change in opposite manners, suggesting that the tetragonality degree of the t phase increases whereas the tetragonality degree of the t´ phase decreases. The microhardness and fracture toughness of the as-annealed crystals depend on the Sm2O3 concentration in the solid solutions. The formation of the monoclinic phase in the (ZrO2)1-х(Sm2O3)х crystals with 0.037 ≤ x ≤ 0.05 significantly reduces the microhardness and fracture toughness of the crystals. Annealing of the (ZrO2)0.94(Sm2O3)0.06 crystals triggers more efficient hardening mechanisms and thus increases the fracture toughness of the crystals. We show that air or vacuum annealing of the (ZrO2)0.94(Sm2O3)0.06 crystals increases the fracture toughness of the crystals by 1.5 times as compared with that of the as-grown crystals.

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DOI: 10.3897/j.moem.9.3.113245

Authors: Andrey N. Aleshin, Oleg A. Ruban

Abstract: In this study, we conducted an investigation into the Ag/SnSe/Ge2Se3/W ionic memristor, focusing on the determination of activation energies associated with its two primary operational processes: the formation of conductive filaments and memristor degradation. To ascertain the electrical conductivity of the memristor in both its basic electronic states, a low resistance state and a high resistance state, we constructed current-voltage characteristics. The estimation of activation energy values was carried out employing the Arrhenius law and the provisions of irreversible thermodynamics, with specific reference to Onsager's second postulate. This fundamental concept posits that the growth rate of irreversible component of entropy can be expressed as the summation of products involving fluxes and thermodynamic forces when a system tends towards its equilibrium state. In the context of this study, the equilibrium state of the memristor is defined as the condition at which the memristor can no longer function as a resistive memory cell. Our experimentation involved the application of a flux of Ag+ ions (electromigration). The calculated activation energy values were found to be 0.24 eV for the initial process and 1.16 eV for the latter. These divergent activation energy values indicate the differentiation between the agglomerative mechanism that governs the formation of conductive channels, prevalent in the Ag/SnSe/Ge2Se3/W memristor, and the "conventional" substance transfer mechanism based on a group of point defects that manifests itself during the memristor's degradation.

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DOI: 10.3897/j.moem.9.3.114129

Authors: Viktor V. Kuts, Andrei V. Turutin, Aleksandr M. Kislyuk, Ilya V. Kubasov, Evelina E. Maksumova, Alexander A. Temirov, Mikhail D. Malinkovich, Nikolai A. Sobolev, Yuri N. Parkhomenko

Abstract: Magnetoelectric (ME) composites have a wide range of possible applications, especially as room-temperature sensors of weak magnetic fields in magnetocardiography and magnetoencephalography medical diagnostic equipment. In most works on ME composites, structures are tested in uniform magnetic fields; however, for practical application, detailed knowledge of their behaviour in inhomogeneous magnetic fields (IMFs) is necessary. In this work, we measured IMFs with radial symmetry produced by alternate currents (AC) passing through an individual thin wire upon different placements of an ME sensor. An ME self-biased b-LN/Ni/Metglas structure with a sensitivity to the magnetic field of 120 V/T was created for IMF detection. The necessity of an external biasing magnetic field was avoided by the inclusion of a nickel layer having remanent magnetization. The ME composite shows a non-zero ME coefficient of 0.24 V/(cm · Oe) in the absence of an external DC magnetic field. It is shown that the output voltage amplitude from the ME composite, which is located in an AC IMF, is dependent on the relative position of the investigated sample and magnetic field lines. Maximum ME signal is obtained when the long side of the ME sample is perpendicular to the wire, and the symmetry plane which divides the long side into two similar pieces contains the wire axis. In the frequency range from 400 Hz to 1000 Hz in the absence of vibrational and other noises, the detection limit amounts to (2 ± 0.4) nT/Hz1/2.

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DOI: 10.3897/j.moem.9.3.113479

Authors: Evgeniya V. Zabelina, Nina S. Kozlova, Oleg A. Buzanov

Abstract: Nominally pure lanthanum-gallium tantalate La3Ga5.5Ta0.5O14 crystals doped with aluminum, silicon and gallium oxide to above stoichiometric content have been grown by the Czochralski technique in iridium crucibles in argon and in agron with addition of oxygen atmospheres. The transmittance spectra of the crystals have been measured on a Cary-5000 UV-Vis-NIR spectrophotometer in the 200–800 nm range. Absorption spectra α(λ) have been plotted on the basis of the experimental data. The absorption spectra of the undoped crystals grown in an oxygen-free atmosphere have one weak absorption band at λ ~ 290 nm. The absorption spectra of the crystals grown in an agron with addition of oxygen have absorption bands at λ ~ 290, 360 and 480 nm. We show that for the crystals grown in an oxygen-free atmosphere, gallium doping to above stoichiometric content reduces the intensity of its only λ ~ 290 nm absorption band. Aluminum doping of the La3Ga5.5Ta0.5O14 crystals grown in an oxygen-free atmosphere significantly reduces the intensity of the λ ~ 290 nm absorption band and increases the intensity of the λ ~ 360 and 480 nm bands. Aluminum doping of the La3Ga5.5Ta0.5O14 crystals grown in an oxygen-containing atmosphere reduces the intensity of the λ ~ 360 and 480 nm bands and increases the intensity of the λ ~ 290 nm absorption band. Silicon doping of these crystals significantly reduces the intensity of the λ ~ 480 nm band and also reduces the intensity of the λ ~ 290 and 360 nm bands.

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DOI: 10.3897/j.moem.9.3.111530

Authors: Vitaliy V. Starkov, Ekaterina A. Gosteva

Abstract: Modern understanding of the material science of semiconductor silicon allowed the authors to propose a new concept of the so-called “charge pumping” in the structures of photovoltaic converters or solar cells. This paper presents theoretical estimates of the rate of separation and collection of light-generated charge carriers in the structures of conventional silicon solar cells and charge-pumped solar cells. Relatively cheaper so-called “solar silicon” of p-type conductivity is typically used in the industrial production of solar cells. This type of silicon is particularly prone to the formation of thermodonor centers. Partial or, at higher temperatures (about 400 °C), even complete overcompensation of the hole type of conductivity in the base region may occur as a result of prolonged heating. This paper presents an original model describing the local formation of n+ regions in the solar cell structure by the so-called “local photon annealing”. These regions were named “charge pumps”. Experimental data on the formation of n+ regions as a result of Li diffusion are reported as an experimental confirmation of the theoretical estimations made in this work. Comparative volt-ampere characteristics of experimental charge-pumped photovoltaic converters and conventional solar cells are presented, showing an up to 30% increase in the short-circuit current Js.c for the experimental structures under standard illumination (AM1.5). The proposed technological aspects of charge-pumped photovoltaic converter fabrication deliver a cheap process and can be implemented in the industrial production of solar cells with little effort.

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DOI: 10.3897/j.moem.9.2.109923

Authors: Vladimir V. Sleptsov, Lev V. Kozhitov, Anna O. Diteleva, Dmitry Yu. Kukushkin, Alena V. Popkova

Abstract: Physicochemical fundamentals have been developed for the basic design solutions and fabrication technologies of prospective electrolytic power cells with a reusable cell capacity of 350–500 W·h/kg at the first stage and 1000 W·h/kg at the second stage. Along with conventional chemical current sources and ionistors, there are emerging high-performance supercapacitor structures with thin dielectric in the double electric layer and hybrid capacitors in which energy is accumulated in the double electric layer and due to electrochemical processes. This approach reduces the internal resistance of the electrolytic cells thus decreasing the heat emission during operation and therefore providing for a higher specific energy capacity and operation safety, shorter charging time and an increase in specific power. Prospective anode is a nanostructured electrode material in the form of a carbon matrix filled with a nanostructured chemically active material. Promising carbon matrix fillers are Li and its alloys, Si, Al, Na, Sn, Mg, Zn, Ni, Co, Ag, as well as a range of other materials and their compounds. The effect of carbon material specific surface area, dielectric permeability and chemically active material addition on the specific energy capacity has been studied. Theoretical specific energy capacity of metal/air hybrid capacitors has been calculated. Thin-film technological system has been designed for new generation electrode materials in the form of carbon matrices with highly developed surface containing thin tunneling dielectrics and chemically active materials on dielectric surface.

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DOI: 10.3897/j.moem.9.2.109827

Authors: Aliaksei V. Pashkevich, Alexander K. Fedotov, Eugen N. Poddenezhny, Liudmila A. Bliznyuk, Vladimir V. Khovaylo, Vera V. Fedotova, Andrei A. Kharchenko

Abstract: The thermal, electrical and thermoelectric properties of ZnO–MexOy ceramics with 1 ≤ x, y ≤ 3, where Me = Al, Co, Fe, Ni, Ti, have been studied. The specimens have been synthesized using the ceramic sintering technology from two or more oxides in an open atmosphere with annealing temperature and time variation. The structural and phase data on the ceramics have shown that post-synthesis addition of MexOy doping powders to wurtzite-structured ZnO powder causes Znx (Mе)yO4 spinel-like second phase precipitation and a 4-fold growth of ceramics porosity. Room temperature heat conductivity studies have testified to predominant lattice contribution. A decrease in the heat conductivity upon doping proves to be caused by phonon scattering intensification due to the following factors: size factor upon zinc ion substitution in the ZnO lattice (wurtzite) by MexOy doping oxide metal ions; defect formation, i.e., point defects, grain boundaries (microstructure refinement); porosity growth (density decline); secondary phase particle nucleation (Znx (Mе)yO4 spinel-like ones). The above listed factors entailed by zinc ion substitution for metal ions (Co, Al, Ti, Ni, Fe) increase the figure-of-merit ZT by four orders of magnitude (due to a decrease in the electrical resistivity and heat conductivity coupled with a moderate thermo-emf decline). The decrease in the electrical resistivity originates from a more homogeneous distribution of doping metal ions in the wurtzite lattice upon longer annealing which increases the number of donor centers.

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DOI: 10.3897/j.moem.9.2.109743

Authors: Aleksandr G. Belov, Vladimir E. Kanevskii, Evgeniya I. Kladova, Stanislav N. Knyazev, Nikita Yu. Komarovskiy, Irina B. Parfent'eva, Evgeniya V. Chernyshova

Abstract: The optical and electrical properties of zinc-doped Cz p-GaAs have been studied. Reflection spectra of ten p-GaAs specimens have been taken in the mid-IR region. Van der Pau galvanomagnetic, electrical resistivity and Hall coefficient measurements have been carried out for the same specimens (all the measurements were carried out at room temperature). The reflection spectra have been processed using the Kramers–Kronig relations, spectral dependences of the real and imaginary parts of the complex dielectric permeability have been calculated and loss function curves have been plotted. The loss function maximum position has been used to calculate the characteristic wavenumber corresponding to the high-frequency plasmon-phonon mode frequency. Theoretical calculations have been conducted and a calibration curve has been built up for determining heavy hole concentration in p-GaAs at T = 295 K based on known characteristic wavenumber. Further matching of the optical and Hall data has been used for determining the light to heavy hole mobility ratio. This ratio proves to be in the 1.9–2.8 range which is far lower as compared with theoretical predictions in the assumption of the same scattering mechanism for light and heavy holes (at optical phonons). It has been hypothesized that the scattering mechanisms for light and heavy holes differ.

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DOI: 10.3897/j.moem.9.2.109980

Authors: Konstantin V. Feklistov, Aleksey G. Lemzyakov, Alexander A. Shklyaev, Dmitry Yu. Protasov, Alexander S. Deryabin, Evgeny V. Spesivsev, Dmitry V. Gulyaev, Alexey M. Pugachev, Dmitriy G. Esaev

Abstract: In2O3 : Er films have been synthesized on silicon substrates by RF magnetron sputter deposition. The currents through the synthesized metal/oxide/semiconductor (MOS) structures (Si/In2O3 : Er/In-contact) have been measured for n and p type conductivity silicon substrates and described within the model of majority carrier thermoemission through the barrier, with bias voltage correction to the silicon potential drop. The electron and hole injection barriers between the silicon substrate and the film have been found to be 0.14 and 0.3 eV, respectively, by measuring the temperature dependence of the forward current at a low sub-barrier bias. The resulting low hole injection barrier is accounted for by the presence of defect state density spreading from the valence band edge into the In2O3 : Er band gap to form a hole conduction channel. The presence of defect state density in the In2O3 : Er band gap is confirmed by photoluminescence data in the respective energy range 1.55–3.0 eV. The band structure of the Si/In2O3 : Er heterojunction has been analyzed. The energy gap between the In2O3 : Er conduction band electrons and the band gap conduction channel holes has been estimated to be 1.56 eV.

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DOI: 10.3897/j.moem.9.2.108161

Authors: Maxim V. Silibin, Dmitry A. Kiselev, Sergey I. Latushko, Dmitry V. Zheludkevich, Polina A. Sklyar, Dmitry V. Karpinsky

Abstract: The crystal structure, piezoelectric and magnetic properties of BiMn1-xFexO3 (x ≤ 0.4) solid solutions synthesized using different solid state reactions from a stoichiometric mixture of simple oxides at high pressures and temperatures have been studied. The structure of the composition undergoes a concentration phase transition from the monoclinic to the orthorhombic structure. The formation of the orthorhombic phase is observed at the concentration x ≈ 0.2 and is accompanied by the destruction of the dz2 orbitals of the Mn3+ ions causing the stabilization of a homogeneous magnetic state. The solid solutions containing 0.2 ≤ x ≤ 0.4 exhibit a non-zero piezoresponse and may have ferroelectric or magnetic domain structures, the ferroelectric switching voltage decreasing with an increase in the iron concentration while the remanent magnetization decreases. The highest piezoresponse signal is observed for the BiMn0.7Fe0.3O3 solid solution. The relationship between the chemical composition, type of crystal structure, piezoelectric and magnetic properties of the BiMn1-xFexO3 solid solutions has been verified. Due to the combination of magnetic and electric dipole ordering these materials show good promise for practical applications.

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DOI: 10.3897/j.moem.9.1.104830

Authors: Izatullo N. Ganiev, Jamshed H. Jayloev, Ermakhmad J. Kholov, Nargis I. Ganieva

Abstract: The design of new materials intended for operation under severe conditions faces the task of rendering the materials corrosion resistant. The practical solution of this task is interrelated with the knowledge of corrosion protection of metals and alloys. The use of conducting aluminum alloys for the manufacture of thin wire may encounter specific problems. This is caused by the insufficient strength of these alloys and a small number of kinks before fracture. Aluminum alloys have been developed in recent years which even in a soft state have strength characteristics that allow them to be used as a conductive material. The E-AlMgSi (Aldrey) aluminum alloy is a well-known conducting alloy. This alloy is a heat-strengthened one, possessing good plasticity and high strength. After appropriate heat treatment this alloy acquires high electrical conductivity. Wires made from this alloy are almost exclusively used for air transmission lines. This work presents data on the corrosion behavior of calcium containing E-AlMgSi (Aldrey) aluminum conducting alloy in 0.03, 0.3 and 3.0% NaCl electrolyte medium. The anodic behavior of the alloy has been studied using a potentiostatic technique with a PI-50-1.1 potentiostat at a 2 mV/s potential sweep rate. Calcium doping of the E-AlMgSi (Aldrey) aluminum alloy increases its corrosion resistance by 15–20%. The corrosion, pitting and repassivation potentials of calcium doped alloys shift toward the positive region. An increase in the sodium chloride electrolyte concentration leads to a decrease in these potentials.

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DOI: 10.3897/j.moem.9.1.103652

Authors: Nikolay A. Kalanda, Marta V. Yarmolich, Alexander V. Petrov, Olga Yu. Ponomareva, Karine K. Abgaryan, Nguyen Huy Dan

Abstract: In this article, a consistent study of phase transformations during the crystallization of YBa2Cu3O7-δ compound was carried out using XRD, thermogravimetric and differential thermal analyzes, as well as optical microscopy. When studying the microstructure and elemental composition in the reaction zone in the process of obtaining single crystals by the crucible-less method, the products of chemical reactions were identified depending on the composition of the reacting components and synthesis conditions. It has been established that the use of precursors Y2BaCuO5, YBa4Cu3O9-δ and ВаCu2O2 as initial reagents has made it possible to carry out the direct synthesis of YBa2Cu3O7-δ single crystals without the formation of intermediate phases. The superconductor has been synthesized at 1270 K on single-crystal MgO substrates with the (001) orientation, since their surface is poorly wetted by the melt solution and stimulates the YBa2Cu3O7-δ nucleation process. This ensures the minimum loss of the liquid fraction formed in the sample. The growth conditions for YBa2Cu3O7-δ single crystals have been studied and optimized. It has been experimentally revealed that the use of combined cooling conditions leads to an increase in the size of single crystals and a reduction in the time of their growth without changing the quality and crystal structure. The investigation showed that the largest volume (50 mm3) was achieved for single-phase YBa2Cu3O7-δ single crystals grown at a cooling rate of 0.5 deg/h in the temperature range 1260–1240 K and at a rate of 1.2 deg/h in the range 1240–1210 K. An analysis of the Laue rotation lines obtained in this work indicates the presence of blocks in single crystals cooled in the temperature range 1243–1193 K at a cooling rate of 1.5 deg/h and their absence in crystals cooled at 1.2 deg/h. An assessment of the degree of perfection of the structure by the width of the rocking curves at half-height of the X-ray reflection (006) showed that the width of the rocking curves of 0.36 deg indicates the absence of structural defects, such as twins, blockiness, and shear defects.

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DOI: 10.3897/j.moem.9.1.104020

Authors: Evgeniya V. Zabelina, Nina S. Kozlova, Oleg A. Buzanov, Elena D. Krupnova

Abstract: Single crystal calcium molybdate CaMoO4 is a well-known material. However the interest to CaMoO4 has recently grown due to a number of its important applications including as a working material in cryogenic scintillation bolometers. CaMoO4 single crystals acquire blue color during growth due to the presence of color-center type defect centers which are unacceptable for optical applications. Color can be eliminated through annealing in an oxygen containing atmosphere, following which required optical components can be produced from the single crystals by mechanical treatment (cutting, polishing etc.). Therefore assessment of the mechanical properties of these single crystal materials is an important task for the optimal solution of issues occurring in the fabrication of optical components and their further practical application. There are but scarce data on the mechanical properties of CaMoO4, and the available ones have been reported without allowance for anisotropy. There is a significant scatter of data on the Mohs hardness of the single crystals, ranging from 3.3 to 6 in different publications. In this work we present data on calcium molybdate single crystals in the initial state and after high-temperature anneals of different durations in an oxygen containing atmosphere. We show that long-term annealing leads to decolorization of the crystals. Calcium molybdate single crystals prove to be quite brittle: the brittleness index Zp of the crystals in the initial state is the highest and equals 5, while annealing reduces the brittleness index to 4. The Palmqvist toughness factors S have been calculated The limit indentation destruction loads Flim have been determined and annealing in an oxygen containing atmosphere has been shown to increase Flim by 2.5 times for the Z cut and by 10 times for the X cut. The microhardness of the crystals has been shown to exhibit a II type anisotropy: the microhardness of all the specimens was higher for the Z cut than for the X cut. The microhardness anisotropy coefficients KH of the specimens have been evaluated. The bond ionicity degree I has been calculated on the basis of the experimentally measured microhardness.

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DOI: 10.3897/j.moem.9.1.103598

Authors: Igor I. Maronchuk, Daria D. Sanikovich, Elena V. Davydova, Nataliya Yu. Tabachkova

Abstract: Problems of the synthesis of cadmium telluride powders having required purity and grain size distribution for high-efficiency solar cells have been analyzed. A test batch of powders has been synthesized and used for the manufacture and study of thin-film solar cell specimens exhibiting parameters compliant with the best worldwide standards. The phase composition of the powders has been studied using X-ray diffraction. Structural analysis and elemental composition measurements have been carried out using electron microscopy. The effect of free tellurium phase in the powders on the endurance of devices manufactured from the powder has been described. We show that excess tellurium in the film specimens whose atoms are predominantly localized along grain boundaries may cause temporal degradation of the electrical properties of the manufactured solar cells due to changes in the parameters of the crystalline structure of the cadmium telluride phase which are caused in turn by changes in the stoichiometric composition of the material. Structural studies of the film specimens have not revealed differences in the film structure before and after endurance tests. A new cadmium telluride powder process route has been developed, proven and tested taking into account the advantages and drawbacks of the previously used process and experiments confirming the correctness of the technical solutions chosen have been conducted.

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DOI: 10.3897/j.moem.9.1.104721

Authors: Dmitriy G. Muratov, Lev V. Kozhitov, Irina V. Zaporotskova, Alena V. Popkova, Vitaly A. Tarala, Evgenij Yu. Korovin, Artem V. Zorin

Abstract: FeCoCu ternary nanoparticles distributed and stabilized in the carbon matrix of FeCoCu/C metal-carbon nanocomposites have been synthesized using controlled IR pyrolysis of precursors consisting of the “polymer / iron acetylacetate / cobalt and copper acetates” type system obtained by joint dissolution of components followed by solvent removal. The effect of the synthesis temperature on the structure, composition and electromagnetic properties of the nanocomposites has been studied. By XRD was shown that the formation of the FeCoCu ternary nanoparticles occurs due to the interaction of Fe3С with the nanoparticles of the CoCu solid solution. An increase in the synthesis temperature leads to an increase in the size of the metal nanoparticles due to their agglomeration and coalescence as a result of matrix reconstruction. Furthermore, ternary alloy nanoparticles having a variable composition may form depending on the synthesis temperature and the content ratio of the metals. Raman spectroscopy has shown that the crystallinity of the carbon matrix of the nanocomposites increases with the synthesis temperature. The frequency responses of the relative permittivity and permeability of the nanocomposites have been studied at 3–13 GHz. It has been shown that a change in the content ratio of the metals noticeably increases both the dielectric and the magnetic losses. The former loss is caused by the formation of a complex nanostructure of the nanocomposite carbon matrix while the latter one originates from an increase in the size of the nanoparticles and a shift of the natural ferromagnetic resonance frequency to the low-frequency region. The reflection loss has been calculated using a standard method from the experimental data on the frequency responses of the relative permittivity and permeability. It has been shown that the frequency range and the absorption of electromagnetic waves (from –20 to –52 dB) can be controlled by varying the content ratio of the metals in the precursor. The nanocomposites obtained as a result of the experiment deliver better results in comparison with FeCo/C nanocomposites synthesized under similar conditions.

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DOI: 10.3897/j.moem.8.4.100756

Authors: Yuri N. Parkhomenko, Aleksandr G. Belov, Elena V. Molodtsova, Roman Yu. Kozlov, Svetlana S. Kormilitsina, Eugene O. Zhuravlev

Abstract: The concentrations of conduction electrons in n-GaSb at 295 and 77 K have been calculated taking into account the non-parabolic deviation of the conduction band shape. We show that at T = 295 K the concentration of heavy electrons in the L-valley of the conduction band is higher than the concentration of light electrons in the Г-valley. On the contrary, at T = 77 K the conduction electrons are mostly concentrated in the Г-valley. Hall data for tellurium doped CZ n-GaSb specimens have been reported. Analysis of experimental data for T = 295 K requires the existence of two types of electrons be taken into account (the light and the heavy ones), the concentrations of which cannot be determined. The apparent increase in the electron concentration with a decrease in the temperature from 295 to 77 K is not true. The concentration of conduction electrons at T = 77 K can be measured correctly with the Hall method.

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DOI: 10.3897/j.moem.8.4.98919

Authors: Andrey V. Sabluk, Alexey A. Basharin

Abstract: Since the early 1980s the terahertz range (0.1 to 10 THz) attracts permanent attention of fundamental and applied science. Due to its unique properties terahertz radiation is used in a wide range of applications such as spectroscopy, non-destructive defectoscopy and security systems. The design of high-efficiency terahertz absorbers and converters is currently the main task in the development of terahertz technologies. In this work a frequency selective high-Q metamaterial is used for the fabrication of a terahertz-to-infrared converter. The converter consists of a metamaterial-based terahertz absorber coated with a micrometer-thick graphite layer that reemits the absorbed energy in the infrared range. We have carried out electrodynamic and the related thermodynamic calculations of the suggested radiation converter. Numerical simulations yield an electromagnetic radiation absorption coefficient of 99.998% and an analytically calculated converter efficiency of 93.8%. Thanks to these advanced parameters suggested terahertz converter can find it’s applications in a wide range of transportation security inspection and defectoscopy tasks.

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DOI: 10.3897/j.moem.8.4.99385

Authors: Stanislav N. Knyazev, Aleksandr V. Kudrya, Nikita Yu. Komarovskiy, Yuri N. Parkhomenko, Elena V. Molodtsova, Vyacheslav V. Yushchuk

Abstract: The development pace of advanced electronics raises the demand for semiconductor single crystals and strengthens the requirements to their structural perfection. Dislocation density and distribution pattern are most important parameters of semiconductor single crystals which determine their performance as integrated circuit components. Therefore studies of the mechanisms of dislocation nucleation, slip and distribution are among the most important tasks which make researchers face the choice of suitable analytical methods. This work is an overview of advanced methods of studying and evaluating dislocation density in single crystals. Brief insight has been given on the main advantages and drawbacks of the methods overviewed and experimental data have been presented. The selective etching method (optical light microscopy) has become the most widely used one and in its conventional setup is quite efficient in the identification of scrap defects and in dislocation density evaluation by number of etch pits per vision area. Since the introduction of digital light microscopy and the related transfer from image analysis to pixel intensity matrices and measurement automation, it has become possible to implement quantitative characterization for the entire cross-section of single crystal wafers and analyze structural imperfection distribution pattern. X-ray diffraction is conventionally used for determination of crystallographic orientation but it also allows evaluating dislocation density by rocking curve broadening in double-crystal setup. Secondary electron scanning electron microscopy and atomic force microscopy allow differentiating etch patterns by origin and studying their geometry in detail. Transmission electron microscopy and induced current method allow obtaining micrographs of discrete dislocations but require labor-consuming preparation of experimental specimens. X-ray topography allows measuring bulky samples and also has high resolution but is hardly suitable for industry-wide application due to the high power consumption of measurements. Digital image processing broadens the applicability range of basic dislocation structure analytical methods in materials science and increases the authenticity of experimental results.

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DOI: 10.3897/j.moem.8.4.98951

Authors: Viktor V. Kuts, Andrei V. Turutin, Aleksandr M. Kislyuk, Ilya V. Kubasov, Roman N. Zhukov, Alexander A. Temirov, Mikhail D. Malinkovich, Nikolai A. Sobolev, Yuri N. Parkhomenko

Abstract: The effect of annealing in a permanent magnetic field on the magnitude of magnetoelectric coefficient in three-layered gradient magnetoelectric LiNbO3/Ni/Metglas composites has been studied. A method of electrochemical nickel deposition on bidomain lithium niobate crystals has been demonstrated. We show that the optimum annealing temperature in a permanent magnetic field for the generation of the highest remanence in the Ni layer is 350 °C. The specimens annealed at this temperature exhibit the greatest shift of the magnetoelectric coefficient dependence on external magnetic field magnitude relative to the value Hdc = 0. The quasi-static magnetoelectric coefficient in the absence of an external magnetic field proves to be 1.2 V/(cm ∙ Oe). The highest magnetoelectric coefficient that has been achieved at a bending structure resonance frequency of 278 Hz proves to be 199.3 V/(cm ∙ Oe) without application of an external magnetic field. The experimental magnetoelectric coefficient figures for three-layered gradient LiNbO3/Ni/Metglas composites are not inferior to those for most magnetoelectric composite materials reported earlier.

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DOI: 10.3897/j.moem.8.4.100653

Authors: Olga V. Boiprav, Natalia V. Bogush

Abstract: An improved technology of frequency-selective electromagnetic shields has been considered. The technology has been improved by embedding classic Archimedean helical elements made from foiled materials into the bulk of the shields for the improvement of the frequency-selective performance of the shields and pinning of these elements in the bulk of the shields by means of fusion bonding. These design features provide for the main advantage of the improved technology in comparison with counterparts, i.e., lower time consumption. The technology has been improved in the following two aspects: 1) identification of helical element parameters providing for the greatest energy loss of the UHF electromagnetic radiation interacting with the helical elements; 2) identification of the optimum helical element arrangement in the shield bulk providing for the smallest transmission and reflection coefficient of the UHF electromagnetic radiation by the shields. Technology improvement in accordance with the former of the above aspects has been achieved based on analysis of publications dealing with mathematical simulation and study of the parameters of UHF electromagnetic radiation transmission by planar helical antennas. Technology improvement in accordance with the latter aspect has been achieved based on experimental data. Test shields have been fabricated with specifically arranged embedded helical elements, and comparison has been made between the UHF electromagnetic radiation transmission and reflection coefficients of the shields. Shields fabricated in accordance with the improved technology suggested herein show good promise for the electromagnetic noise protection of electronic devices.

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DOI: 10.3897/j.moem.8.3.98758

Authors: Alexander L. Gurskii, Nikolay A. Kalanda, Marta V. Yarmolich, Alexander V. Petrov, Petr N. Kireev, Deleg Sangaa, Ping-Zhan Si

Abstract: Based on the data of thermogravimetric analysis the values of the oxygen index (3-δ) in the manganite of the La0.7Sr0.3Mn0.9Fe0.1O3-δ composition, obtained by solid-phase reaction technique, have been calculated. The analysis of oxygen sorption-desorption curves showed that the processes of oxygen release and absorption at pO2 = 10 Pa and pO2 = 400 Pa are not reversible. The minima of the derivative dδ/dt = f (T) corresponding to the maxima of the oxygen extraction rate indicate the complex character of changes in the oxygen desorption rate from manganite. The decrease in the heating and cooling rate from 6.6 K/min to 2.6 K/min resulted in a significant change in the value ∆δ, indicating the dependence of anion mobility on the oxygen concentration in the magnet structure. It has been revealed that in the La0.7Sr0.3Mn0.9Fe0.1O3-δ manganite the oxygen desorption kinetics is well described by the exponential dependence on the Kramers model, which implies no return of desorbed oxygen to the sample. This model indicates the non-stationarity of the diffusion flux through the barrier during desorption of oxygen from samples. The calculation of the activation energy of oxygen desorption by the Merzhanov method at various partial pressures of oxygen has shown that at the initial stage of oxygen extraction from La0.7Sr0.3Mn0.9Fe0.1O3-δ, the activation energy of oxygen desorption has a minimum value (Еа = 103.7 kJ/mol at δ = 0.005) and as the concentration of oxygen vacancies increases, it rises reaching saturation (Еа = 134.3 kJ/mol at δ = 0.06). It is assumed that with an increase in the concentration of oxygen vacancies, an interaction occurs between them, followed by the processes of their ordering with the formation of associates.

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DOI: 10.3897/j.moem.8.3.98145

Authors: Andrey A. Orlov, Askar A. Rezvanov

Abstract: In this work, the simulation of the processes of diffusion of metal barrier ions into a low-k dielectric between two nearby copper lines was performed. Based on experimental data on the diffusion coefficient published in the scientific literature and calculations according to the mathematical model of the distribution of metal barrier ions in the dielectric, the time dependent breakdown of a porous low-k dielectric in the elements of very large-scale integrated circuits of the modern topological level was estimated. Additionally, the work obtained dependences of the dielectric breakdown time on the distance between two nearby copper lines along with dependence on the power voltage of the line (the other line is grounded).

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DOI: 10.3897/j.moem.8.3.98706

Authors: Lyudmila V. Tarala, Alexander A. Kravtsov, Oleg M. Chapura, Vitaly A. Tarala, Dmitry S. Vakalov, Fedor F. Malyavin, Sergey V. Kuznetsov, Viacheslav A. Lapin, Lev V. Kozhitov, Alena V. Popkova

Abstract: The aim of this work was to study the effect of vacuum sintering conditions and cerium concentration on the optical, luminescent and thermal properties of yttrium-aluminum garnet based ceramics doped with Се3+ cations. Series of ceramic powders were synthesized and samples of luminescent ceramics having the composition Y3-хСехAl5O12 were synthesized where x was in the range 0.01 to 0.025 f.u. We show that the phase composition and grain size distribution of the ceramic powders do not depend on cerium concentration. Without sintering additives, an increase in vacuum sintering temperature from 1675 to 1800 °C leads to an increase in the optical transmittance of luminescent ceramic specimens from 5 to 55% at a 540 nm wavelength and an increase in the thermal conductivity of the samples from 8.4 to 9.5 W/(m ∙ K). It was found that an increase in cerium concentration leads to a shift of the luminescent band peak from 535 to 545 nm where as the width of the luminescent band decreases with an increase in vacuum sintering temperature from 1675 to 1725 °C.

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DOI: 10.3897/j.moem.8.3.97596

Authors: Vladimir N. Abryutin, Igor I. Maronchuk, Nikolai A. Potolokov, Daria D. Sanikovich, Natalia I. Cherkashina

Abstract: Simulation data have been presented on a process of deep refinement of tellurium based on Authors-developed refinement technique implemented through analysis of the process unit thermodynamical condition using Flow Simulation software, from SolidWorks software product. The technique put forward herein has been implemented in a plant comprising a vertical air-tight reaction chamber arranged inside a multi-zone thermal unit and executing a sequence of refinement stages which use different techniques and are integrated in a single process. The experimental data which have been the basis for calculations have allowed one to determine the boundary conditions of the mathematical model taking into account previous operation experience of the software product used. Temperature profile calculation has been carried out taking into account all the types of heat transfer in the system, the weight / dimensions parameters of system units and the physicochemical properties of refined tellurium, materials of equipment fittings and reactor media. The temperature modes of the process stages have been accepted as the boundary conditions for the thermal calculations, with temperatures being measured at equipment fitting locations at which temperature gages connected with a PID controller have been installed. The simulation of specific refinement process conditions allowed process modes and equipment fitting component design to be corrected. We have developed and produced test models of process and imitation equipment. Analysis of the thermal fields for the final model has shown good agreement with the mathematical model. Equipment upgrading and process parameter improvement on the basis of the simulation results have allowed T-u Grade tellurium (99.95 wt.%) refinement to a 99.99992 wt.% purity by 30 main impurities in the course of physical experiments, the product yield being at least 60%.

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DOI: 10.3897/j.moem.8.3.91521

Authors: Barham K. Rahim, Fahmi F. Muhammadsharif, Salah R. Saeed, Kamal A. Ketuly

Abstract: In this paper, the optical properties and optoelectronic parameters of two newly synthesized polymers forming a donor : acceptor (D : A) binary system are investigated, followed by their subsequent doping with Sudan dye to obtain a ternary system. The donor polymer is P(TER-CO-TRI), while the acceptor is poly(5-hydroxy-L-Tryptophane). A cost-effective solution-processing was carried out to obtain different binary and ternary composites with concentration of 0.5 mg/ml. Optical absorption spectroscopy was used to measure the optical response and optoelectronic parameters, while FTIR and cyclic voltammetry were used to assess the structure and molecular energy levels of the polymers. The results revealed that the non-dispersive refractive index and energy gap of binary D : A was decreased from 1.56 to 1.52 eV and from 2.84 to 2.10 eV, respectively, when it was doped with Sudan dye. It was concluded that with the help of doping process, different values of energy band gap, refractive index, dielectric constant, and optical conductivity are achieved. This tuning achievement of the optoelectronic parameters is crucial in determining the possible applications of these materials in the organic electronics, photodiodes and photovoltaic devices.

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DOI: 10.3897/j.moem.8.2.97508

Authors: Vladimir V. Sleptsov, Anna O. Diteleva, Dmitry Yu. Kukushkin, Roman A. Tsyrkov, Elizaveta O. Diteleva

Abstract: A method for the formation of metal nanoparticles in a localized volume with a high energy density due to the flow of a pulsed electric discharge and the cavitation effect was studied. The mechanism of the formation of energy inhomogeneities providing for the generation of nanoparticles with a high specific energy intensity was considered. Dynamic heterogeneity forms in three stages. There is a breakdown of the inter-electrode gap and the formation of a vacuum volume filled with a vapor-gas medium. When the pressure inside the bubble increases, a pulsed gas discharge is ignited, thus generating metal nanoparticles. This leads to the formation of a localized volume in which the discharge energy reaches values of up to 106 K. The increase in energy in the bubble leads to its collapse, after which the metal nanoparticles pass from the high-energy (106) medium into water at room temperature, resulting in their hardening. Highly pure nanoparticles of various metals 5–15 nm in size are obtained; these can be grown on a single-crystal silicon surface at room temperature and positioned on the surface of porous materials and products of complex configuration.

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DOI: 10.3897/j.moem.8.2.90062

Authors: Serekbol Zh. Tokmoldin, Vasiliy V. Klimenov, Dmitriy V. Girin, Nikolay A. Chuchvaga, Kazybek P. Aimaganbetov, Musabek P. Kishkenebaev, Svetlana N. Tarakanova, Nurlan S. Tokmoldin

Abstract: Mathematical simulation of temperature distribution on double-sided solar cells has been carried out. Differences in the configuration of photoelectric converters prove to solely amount to the fact that a double-sided solar cell has a more efficient heat sink at the rear side. Furthermore double-sided solar cells exhibit higher power conversion performance. Calculations confirm the correctness of giving preference to double-sided solar cells which is of great importance for the photoelectric converter design developed by us. Analysis of market-available photovoltaic technologies of solar energy to electric power conversion has led to the development of a photovoltaic converter on the basis of double-sided silicon heterojunction solar cells. The configuration developed is a moving platform having a photovoltaic cell array mounted on it and a light flux collector. A double-axis tracking system has been developed for the general case of planar attachment of solar cell modules. A 350 mm stroke drive provides for movement in the north-south direction and a 450 mm stroke drive, in the east-west direction. The task has been outlined to find the required arm for providing symmetrical positioning at the maximum rotation angle about the axis. As a result, technical solutions have been developed for the north-south and the east-west directions. Furthermore a schematic wiring diagram has been designed to implement the preset solar tracking system algorithm. The system is also fitted with a GPS/GLONASS module for system precision positioning and time synchronization.

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DOI: 10.3897/j.moem.8.2.97723

Authors: Izatullo N. Ganiev, Ermakhmad J. Kholov, Jamshed H. Jayloev, Nargis I. Ganievа, Vladimir Dz. Abulkhaev

Abstract: In the development of new materials designed for use under particularly harsh conditions, the task of making them corrosion-resistant arises. The practical solution to this task correlates with knowledge in the field of high-temperature oxidation of metals and alloys. When using conductive aluminum alloys for the production of fine wires, such as winding wire, certain difficulties may arise due to their insufficient mechanical strength and inflection before breaking. The solution of modern technological problems is associated with the use of highly oxidation- resistant materials. As a consequence, the study of the interaction of oxygen with metals and alloys has become very important due to the widespread use of new materials with special physical and chemical properties. The E-AlMgSi (Aldrey) aluminum conductive alloy occupies a special place among others. The oxidation process of the alloys was studied under isothermal air atmosphere by thermogravimetric method with continuous fixation of the sample mass for 1 h at temperatures of 723, 773 and 823 K. The oxidation kinetics curves and the value dependencies of the specific mass increase of cadmium in the E-AlMgSi (Aldrey) alloy quantity, time and temperature were constructed on the experimental data basis. The processing of the quadratic kinetic curves of the oxidation of the alloys at the above temperatures has shown that the oxidation of the alloys obeys the hyperbolic dependence y = kxn, where the value of n varies from 1 to 4. The lg k dependence on 1/T for the alloy E-AlMgSi (Aldrey) with cadmium shows that the oxidation rate increases with temperature and cadmium content increasing.

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DOI: 10.3897/j.moem.8.2.84239

Authors: Nina S. Kozlova, Evgeniy A. Levashov, Philipp V. Kiryukhantsev-Korneev, Alina D. Sytchenko, Evgenia V. Zabelina

Abstract: Ta–Si–C–N single-layer films have been synthesized by direct current magnetron sputtering on fused quartz substrates. The structural perfection of the films has been studied using X-ray diffraction, scanning electron microscopy and glow discharge optical emission spectroscopy. The optical parameters of the films have been studied using multi-angle spectrophotometry. The spectral dependences of the transmission coefficients of substrates and structures were measured for normal incidence of light in the wavelength range 200–2500 nm. We show that the transmittance spectrum of the specimen has an oscillating pattern due to interference phenomena that are typical for layered structures. The reflectance of the films and the substrates has been measured in the 200–2500 nm region for small incidence angles. The difference between the reflection coefficient at the maximum of the interference of the film and the corresponding reflection coefficient of the substrate at the same wavelength shows that the absorption in the film is low. A formula for determination of the film absorption index based on the measured parameters has been derived. The experimental and calculated data have been used for plotting the absorption spectra of the substrate, structure and film. Discrete refractive indices in the 400–1200 nm region have been calculated for reflections at two incidence angles by determining the positions of interference maxima in the reflectivity spectral responses. The results have been approximated using the Cauchy equation. The film thickness has been estimated to be df = 1046 nm ± 13%. The spectra of film extinction coefficients have been plotted with and without allowance for reflection. Obtained values of the refractive and absorption indices with and without reflection have been summarized in a table.

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